AAS 2005 Meeting logo

Abstracts

2005 Annual Meeting
at the University of Akron

June 27 to 30

Hosted by

Maggie Hodge
Todd Blackledge
Sam Marshall 

 

Use the table below to jump to abstracts, alphabetized by first author

A, B and C

Screening of necrotizing arachnidism in Korea using sphingomyelinase assay

Authors
Institution

Jeong-Su An

Department of Biological Sciences
Dankook University,
Cheonan 330-714, KOREA

Yong-Seok Choi
Myung-Jin Moon

Abstract: While spider bites are not a major medical problem in Korea, it would be of great value to know which species of spiders pose a threat to human health. There are now more than 40,000 identified spider species in the world, and considered about 100 species as actually dangerous to human. Spider bites cause a range of symptoms from simple swellings to disfiguring necrotic lesions, and occasionally death. A middle molecular weight protein, sphingomyelinase D, has been identified in the venom of the brown recluse spider and strong evidence suggests that they have a major role in spider bite necrosis (Tambourgi et al., 1998). For the identification of necrotizing species, we have investigated using recently developed non-radioactive assay of sphingomyelinase for rapidly screening the necrotizing venoms. Here, we demonstrate the fetal toxicity of total 122 species among 622 identified spider species of Korea. It has been revealed that one species of the orb-weaving spider, Araneus ventricosus, and another species of wandering spider, Dolomedes sulfureus has the strongest positive activities among themselves. However comparing to that of the brown recluse spider, Loxosceles reclusa, in North America the necrotizing activities of these Korean species are still very low, so it seems to be little possibilities to create serious necrotizing arachnidism in Korean peninsula. (posted 5 - 24 - 2005)

 

Microstructure of the silk spinnerets in the lynx spider, Oxyopes licenti (Araneae: Oxyopidae)

Authors
Institution

Jeong-Su An

Department of Biological Sciences
Dankook University,
Cheonan 330-714, KOREA

Sung-Moon Yoe
Myung-Jin Moon

Abstract: Lynx spiders are one of free wandering spiders with long legs. They do not build web but hunt small insects on plants. In spite of the facts that the wandering spiders do not produce webs for prey-catching, they also have silk apparatus even though the functions are not fully defined. Here we describe the fine structural organization of the silk glands and its spinning apparatus in the lynx spider, Oxyopes licenti, revealed by the transmission electron microscope (TEM) and field emission scanning electron microscopes (FESEM). The silk glands of the adult female spider were located in four groups on the spinnerets including each pair of major and minor ampullates, tubuliforms, pyriforms and aciniforms. Each group of silk gland feed silk into one of the three pairs of spinnerets. Moreover, the tubuliform gland is only observed in female spiders, and the ampullate one is the most predominate gland in both sexes. However the flagelliform and the aggregate glands which had the function of adhesive thread production in orb-web spiders were not observed at both sexes of this spider. (posted 5 - 24 - 2005)

 

Fluorescence in spiders

Author
Institution

Kindra Andrews

Department of Biology
Portland State University
Portland, OR USA

Susan E. Masta

Abstract: Most studies of the color properties of organisms have focused on the portion of the light spectrum that is visible to humans.  However, many animals are able to detect wavelengths in the ultraviolet range, and recent research with birds has uncovered some surprising patterns of ultraviolet reflectance.  While examining the potential for ultraviolet reflectance in jumping spiders, we discovered that some spider setae also fluoresce when exposed to UV light.  While the fluorescent properties of the scorpion cuticle have been well-documented, fluorescence in other arachnids has not been studied.  Therefore, using an ultraviolet light and a digital camera, we have photographically documented the existence and distribution of fluorescence in spider setae and cuticles from diverse taxa.  We present data from spiders from the families Antrodiaetidae, Theraphosidae, Gnaphosidae, Thomisidae, Clubionidae, Salticidae, Lycosidae, Araneidae, Agelenidae, and Theridiidae.

Because nothing is known of the potential adaptive value of fluorescence in spiders, we have explored correlations between fluorescence and behavioral and ecological traits, such as time of activity (diurnal or nocturnal), prey capture strategies (hunter-wanderer, orb-weaver, or sit-and-wait), and sensory characteristics (visually oriented spiders versus spiders relying more on other senses).  Our studies so far indicate that fluorescent setae are correlated with diurnal activity, but there are complex patterns associated with feeding strategies and visual capabilities.  We discuss the potential evolutionary significance of fluorescence in spiders. (posted 5 - 26 - 2005)

 

Evolution of habitat-use in a desert spider, Agelenopsis aperta

Author
Institution

Nadia Ayoub

Biology Department
University of California
Riverside, California USA

Abstract: In the past, phylogeography has been primarily used to track historical events of species, such as colonization of islands or population fragmentation. A potentially powerful application of phylogeography is to trace the evolutionary history of adaptations to different habitats. The desert spider, Agelenopsis aperta, presents a unique opportunity to complete just such a study. An extensive background database exists for A. aperta on the genetic basis of adaptations to different habitats: arid and riparian. Furthermore, riparian patches are widely distributed throughout the spider's range of the desert southwest United States making migration between patches unlikely. In order to assess whether adaptations arose once and spread throughout the range of A. aperta or arose multiple times via recent natural selection, I used mitochondrial DNA sequences to examine population history of riparian patches and surrounding arid populations distributed across the range of A. aperta. Riparian patches exhibited identical mitochondrial DNA haplotypes to surrounding arid populations. On the other hand, geographically distant populations were genetically distinct. These population genetic patterns indicate that adaptations arose as a result of recent natural selection. (posted 5 - 24 - 2005)

 

An integrative approach to deciphering spider silk evolution

Authors
Institution

Nadia Ayoub

Biology Department
University of California
Riverside, California USA

Cheryl Hayashi

Abstract: Spiders use silk for a variety of tasks throughout their lifetime.  These tasks include safety draglines, prey capture nets, protective retreats, and coverings for eggs.  Some lineages of spiders make only a few general-purpose silks while other lineages synthesize many specialized silks.  Wide interest in spider silks has stemmed from the remarkable mechanical properties of some silks, which possess both extraordinary toughness and extensibility.  Silks are composed of highly repetitive proteins that are encoded by a multi-gene family.  To understand the structure, function, and evolution of spider silk genes, proteins, and fibers, the Hayashi research group takes a three-pronged approach. First, we quantify the biomechanic properties of silk fibers spun by a diversity of species.  Second, we construct cDNA (gene expression) libraries from the silk glands of phylogenetically diverse species to determine the coding sequences of silk proteins. Third, we have built a genomic library (~3X genome coverage, ~40 kilobase insert size) from the Western black widow, Latrodectus hesperus.  We are using this library to characterize silk gene architecture and regulatory regions.  Our various silk genotypic and phenotypic data are integrated within a phylogenetic framework to trace the evolutionary steps that have led to the present diversity of spider silks. (posted 5 - 24 - 2005)

 

A morphometric analysis of mygalomorph carapace shape and its efficacy as a phylogenetic character

Authors
Institution

David Beamer

Department of Biology
East Carolina University
Greenville, NC USA

Jason E. Bond

Abstract: Despite the fact that shape features are often used as characters in cladistic analyses they are seldom delineated in an objective, repeatable fashion.  Carapace shape is one such character that is often used in analyses of mygalomorph spider relationships.  For example, most analyses (Raven 1985, Goloboff 1993, Bond & Opell 2002) use cephalic region morphology (e.g., steeply arched vs. flat or sloping) as a key feature that delineates (in part) some major clades.  In practice carapace shapes at the extremes are relatively easy to identify; however, intermediate carapace shapes have proven to be much more difficult to objectively score in one of three shape categories.  In this study carapace shape is used as an exemplar characteristic to evaluate the utility of shape features in phylogenetic analyses and to evaluate our ability to effectively score discrete character states.  We digitally photographed 173 spider carapaces from specimens sampled across all 15 nominal mygalomorph families and traced outlines and pseudo-landmarks.  An Elliptic Fourier Analysis was then employed in an attempt to both delineate and assess character states. (posted 5- 19 - 2005)

 

The effects of wolf spider communities on soybean herbivory

Authors
Institution

Ryan D. Bell

Biology Department
Susquehanna University
Selinsgrove, Pennsylvania USA

Michael V. Cole

Matthew H. Persons

Alissa A. Packer

Abstract: Wolf spiders are common generalist predators in agricultural systems and could potentially have direct or indirect effects on plant herbivory. Many wolf spiders are also significant intraguild predators that may result in complex interactions between spiders, herbivores, and plants. We conducted a field study using three commonly occurring wolf spiders, Pardosa milvina, Trochosa ruricola, and Rabidosa spp. with soybean as our model agricultural plant.  Nine treatments were created by planting the soybean during the summer growing season within enclosures of different wolf spider communities.  The treatments were: 1) Rabidosa only, 2) Pardosa only, 3) Trochosa only, 4) Pardosa and Rabidosa, 5) Pardosa and Trochosa, 6) Trochosa and Rabidosa, 7) no enclosure, 8) no spiders, and 9) Pardosa, Rabidosa, and Trochosa (N= 17/treatment).  Enclosures were checked on a weekly basis, various vegetative and reproductive measurements were taken.  The presence of spiders was recorded, and any non-treatment species were removed.  Plants were harvested at the end of the summer and leaves, pods, and root nodules were counted and plant biomass was weighed.  Spider treatments were not shown to have a significant impact on any vegetative or reproductive plant traits, but intraguild interactions did impact spider number and body condition, particularly for Pardosa milvina.(posted 5 - 18 - 2005)

 

Molecular phylogenetic analyses of Sicariid species relationships and sphingomyelinase D gene family evolution

Authors
Institution

Greta J. Binford

Department of Biology
Lewis & Clark College
Portland, Oregon, USA

Chris Ellison

Kate Baldwin

Melissa Bodner

Melissa Callahan

Abstract: Loxosceles and Sicarius spiders are well known for the dermonecrotic effects of their venoms on mammalian tissues. The toxic enzyme sphingomyelinase D (SMase D) is sufficient for causing lesion formation after bites from these species. Inspired by a desire to understand the molecular evolution of SMase D we are using sequence data from mitochondrial markers ND1/16s, CO1, and nuclear 28s to estimate relationships among species representing their native distribution. Analyses to date consistently support: (1) North American Loxosceles as monophyletic and their presence on the continent predating the most recent connection of North and South America by the Isthmus of Panama; (2) South African species as basal lineages within both genera. Interestingly, species relationships within Loxosceles do not match the gene tree for SMase D. Patterns of relationships among SMaseD cDNAs make it clear that SMase D evolution includes processes that homogenize paralogs within lineages. We propose differential paralog homogenization as an explanation for the gene tree - species tree mismatch. l.(posted 5 - 18 - 2005)

 

Spider silk: a 400 million year experiment in materials science

Author
Institution

Todd A. Blackledge

Department of Biology
University of Akron
Akron, OH USA

Abstract: Silk plays an integral role in many aspects of the lives of spiders including protection against predators or the environment, capture of prey, dispersal, communication, and reproduction. Thus, the mechanical performance of spider silk is likely to have been shaped by natural selection and can provide insight into how spiders interact with their environment. The material properties of spider silk result from how the constituent proteins of silk fibers are assembled and interact with one another. Therefore, the biomechanical study of spider silk can potentially link together research ranging from the evolution of silk genes through the ecological function of webs or other silk structures. Here, I discuss some of my recent research on the biomechanics of orb-weaving spider silk. In particular, I demonstrate that Argiope argentata spins a diverse toolkit of silks, including five different fibrous silks each of which has its own unique mechanical characteristics. (posted 5 - 24 - 2005)

 

Light wavelength biases of the desert grassland scorpion

Authors
Institution

Greg R.C. Blass

Department of Zoology
University of Oklahoma
Norman, Oklahoma USA

Douglas D. Gaffin

Abstract: Desert grassland scorpions, Paruroctonus utahensis, are nocturnal animals that typically emerge from their burrows within a few hours after sunset.  Scorpions are negatively phototactic, and physiological data suggest that scorpion photoreceptors are differentially sensitive to light wavelengths ranging from red to ultraviolet.  However, behavioral differences to wavelengths have not been firmly established.  Responses of animals were monitored in circular (8.9 cm diameter) arenas.  Half of each arena received infrared light, while the other half received one of four treatments:  red, green, UV, or no light.  The three light treatments were matched for intensity.  We ran three trials of sixteen animals each (48 total animals) with each animal experiencing the full set of randomized treatments; each treatment lasted 1 h for a total filming time of 64 h. Each animal was monitored for periods of movement into and out of the treated side, and these periods were averaged within a 10 min sampling window for each treatment.  Scorpions spent significantly less time in areas exposed to UV than those exposed to green light (P=0.01) or red light (P<0.01).  This does not correlate directly with reported physiological spectral sensitivity of the median and lateral eyes, which indicate peak sensitivity in the green with a lesser but pronounced shoulder in the UV.  These observations may relate to extraocular regions of light sensitivity and/or the green fluorescence of scorpion cuticle under UV.(posted 5- 19 - 2005)

 

Evolutionary origin and loss of sphingomylinase D in the Sicarius and Loxosceles lineages

Authors
Institution

Melissa R. Bodner

Department of Biology
Lewis & Clark College
Portland, OR USA

Melissa Callahan

Greta J. Binford

Abstract: The enzyme sphingomyelinase D (SMaseD) found in the venoms of brown spiders (Loxosceles) causes dermonecrotic lesions in mammalian tissues.  Bites from some species of the related genus Sicarius cause similar lesions.  Previous comparative venom/tissue analyses of representatives from eight families of haplogyne spiders found SMaseD activity only from a worldwide representation of Loxosceles and two South African Sicarius species, supporting evidence of evolutionary origin of SMaseD in the most recent common ancestor of Loxosceles and Sicarius.  This analysis did not include New World representatives of Sicarius.  We report SMaseD assays of venoms of the Costa Rican species Sicarius rugosus and the Argentine species S. patagonicus, S. rupestris and S. terrosus.  Unlike Old World congenerics, all New World Sicarius species showed a reduction or loss of SMaseD activity, yet had proteins of the molecular weight corresponding to SMaseD.  To test whether the differences in New World venom represented an ancestral or derived state, molecular phylogenetic analyses of the relationships among the genera Loxosceles, Sicarius, Drymusa and Scytodes where carried out using a roughly 1.8 kb fragment of 28S.  All analyses placed New World Sicarius as derived from SMaseD bearing ancestors, indicating the apparent loss of SMaseD activity in New World Sicarius is a derived state.  A more thorough survey of Sicarius species will determine whether the reduction or loss of SMaseD activity is universal in and exclusive to the New World lineage. (posted 5 - 20 - 2005)

 

Molecular phylogeny of the Mygalomorphae

Authors
Institutions

Jason E. Bond

Department of Biology
East Carolina University
Greenville, NC USA

Marshal Clinton Hedin
Department of Biology
San Diego State University
San Diego, CA USA

Abstract: Mygalomorph spiders, which include the tarantulas, trapdoor spiders, and their kin, represent one of three main spider lineages.  Current estimates of mygalomorph diversity place roughly 2,500 species into approximately 280 genera and 15 families.  Published phylogenies of mygalomorph relationships, based almost exclusively on morphological data, reveal areas of both conflict and congruence, suggesting the need for additional phylogenetic research.  As part of a combined evidence study of global mygalomorph relationships, we have gathered ~ 4.2 kb of rDNA data (18S and 28S) for a sample of 80 genera, representing all 15 mygalomorph families.  The following primary results are supported by both Bayesian and parsimony analyses of the combined matrices: 1) the Atypoidina, including Atypidae, Antrodiaetidae and Mecicobothriidae, are basal, 2) diplurids and hexathelids form a paraphyletic grade at the base of the remaining tree, but neither family is recovered as monophyletic, 3) sampled nemesiids form a clade, but include Microstigmata and the Australian cyrtaucheniid Kiama, 4) other sampled cyrtaucheniids are separated into two clades, including a North American Euctenizinae and a South African clade, 5) of the Domiothelina, only idiopids are consistently recovered as monophyletic, while (surprisingly) migids and ctenizids are not.  The Domiothelina themselves are not monophyletic.  Overall, the molecular results are more consistent with Goloboff (1993), less consistent with Raven (1985). (posted 5- 25 - 2005)

 

 

Combining genetic and geospatial analyses to infer population extinction in mygalomorph spiders endemic to the Los Angeles region

Authors
Institutions

Jason E. Bond

Department of Biology
East Carolina University
Greenville, NC USA

David Beamer
Marshal Clinton Hedin
Department of Biology
San Diego State University
San Diego, CA USA

Abstract: Although hyperdiverse groups like terrestrial arthropods are almost certainly severely impacted by habitat fragmentation and destruction, relatively few studies have formally documented such effects.  We summarize a multifaceted research approach to assessing the magnitude and importance of anthropogenic population extinction on the narrowly endemic trapdoor spider genus Apomastus (Mygalomorphae: Cyrtaucheniidae).  We use GIS (Geographical Information Systems) modeling to reconstruct the likely historical distribution of Apomastus, and use molecular phylogeographic data to understand population genetic structure and detect genetic signatures of population extinction.  In combination, these complementary lines of inference support direct observations of population extinction, and lead us to conclude that population extinction via urbanization has played an important role in defining the modern-day distribution of Apomastus species.  This population loss implies coincident loss of genetic and adaptive diversity within this genus, and more generally, suggests a loss of ground-dwelling arthropod population diversity throughout the LA Basin.  Strategies for minimizing this loss are proposed. (posted 5- 18 - 2005)

 

The Balkan and Aegean Euscorpius (Scorpiones: Euscorpiidae): new data for mitochondrial DNA phylogeny

Authors
Institutions

Michael Brewer

Department of Biological Sciences
Marshall University
Huntington, West Virginia USA

Victor Fet

Elizabeth V. Fet

Jan Ove Rein

Norwegian University of Science & Technology
Trondheim NORWAY

Marco Colombo

Busto Arsizio
Varese ITALY

Abstract: The systematic composition of the genus Euscorpius Thorell, 1876 (Scorpiones: Euscorpiidae) in the Balkans is unclear. This especially refers to so-called "carpathicus complex" (Fet & Soleglad, 2002). New material obtained in 1999-2004 from Greece and Bulgaria has been used for DNA extraction and PCR amplification of ca. 400 bp of the mitochondrial gene for 16S rRNA, followed by sequence comparison of 26 DNA sequences via PAUP* 4b10. New data for mitochondrial DNA phylogeny allow to outline several independent lineages, some of which could have species status. A separate Greek lineage is formed by populations from Crete ("E. candiota" Birula, 1903) grouping closely with Kithyra, Peloponnese, and western Greece (Corfu and Parga in Epiros). Among other Aegean islands, Thassos population is very different from Paros; the latter shows affinity to E. tauricus (C.L. Koch, 1837) from Crimea, Ukraine. Another cluster is formed by populations from Rhodope Mts. (Xanthi in Northern Greece; Trigrad, Kovachevitsa, and Melnik in Southern Bulgaria). Olympus and Ossa (Thessaly, Eastern Greece) refer to "E. carpathicus ossae" Caporiacco, 1950. Sliven (Stara Planina Mts., Bulgaria) forms a separate lineage, not close to Romanian E. carpathicus (L., 1767); the latter shows affinity to the western Balkan (Slovenia, Croatia)/Italian E. tergestinus (C.L. Koch, 1837). Separate status of the Balkan E. hadzii Caporiacco, 1950 (Croatia, Herzegovina) and E. sicanus (C.L.Koch, 1837) (Thessaly) is confirmed. In total, Greece could house over 10 species of Euscorpius, and Bulgaria, at least four. (posted 5 - 6 - 2005)

 

Arachnological concerns of USDA, APHIS and PPQ (talk)
&
Mouth parts of important tick genera (poster)

Author
Institution

Susan Broda

USDA, APHIS, PPQ
Baltimore MD

Abstract: A preliminary general overview will be given of arachnological groups which are of concern to USDA, APHIS, PPQ, as well as the Homeland Security Department. I will then describe in more detail the problems with exotic ticks (Acarina: Metastigmata) being brought in on exotic pets introduced to the USA. (posted 5 - 16 - 2005)

 

I smell a femme fatale: can males chemically detect a cannibalistic prospective mate?

Authors
Institutions

Joshua M. Cattell

Biology Department, Susquehanna University
Selinsgrove, Pennsylvania USA

Ann L. Rypstra

Department of Zoology, Miami University
Hamilton, Ohio USA

Matthew H. Persons
Biology Department, Susquehanna University
Selinsgrove, Pennsylvania USA

Abstract: Virgin female Hogna helluo wolf spiders cannibalize prospective mates in 13-20% of encounters with courting males.  Males may therefore benefit by possessing the ability to detect and avoid cannibalistic females.  We tested if prior cannibalistic experience alters female behavior toward males and if males can detect cannibalistic females based on either direct interactions with females or indirectly through cues from female silk and excreta. We reared 36 female spiders on entomophagic diets consisting of house crickets (Acheta domesticus) and an additional 34 females on araneophagic diets consisting of two Hogna feedings at adulthood prior to testing.  We then measured male and female mating behavior across the following treatments (14-20 replicates/treatment): 1) cannibalistic female on cannibalistic chemical cues, 2)  cannibalistic female on non-cannibalistic chemical cues, 3)  non-cannibalistic female on non-cannibalistic chemical cues, and 4)  non-cannibalistic female on cannibalistic chemical cues. Male Hogna were placed with females and cannibalism events, courtship duration, courtship latency, mating success, and courtship intensity were recorded. Males significantly decreased courtship duration in the presence of cannibalistic females and significantly increased courtship intensity when encountering silk from females that had cannibalized previously. Cannibalistic females showed higher numbers of leg taps, a putative receptive response, toward males than non-cannibals but we found no significant difference in mating success or cannibalism frequency across treatments.  Results suggest that males discriminate between females who have eaten conspecifics and those who have not based on information in silk, but female cannibalism frequency and male mating success is unrelated to recent female cannibalism experiences. (posted 5 - 13 - 2005)

 

Influences of Environmental Variation on Courtship Behavior in the Wolf Spider Schizocosa ocreata

Authors
Institutions

David L. Clark

Dept. of Biology
Alma College
Alma, MI  48801 USA

George W. Uetz

Dept. of Biology
University of Cincinnati
Cincinnati, OH  45221 USA

J. Andrew Roberts

Department of EEOB
The Ohio State University at Newark
Newark, OH  43055 USA

Meghan Rector

Dept. of Biology, Alma College
Alma, MI  48801 USA

Abstract: During the breeding season, male wolf spiders (Schizocosa ocreata) expend considerable energy searching for females and run a risk of predation by exposing themselves to potential predators.  In the leaf litter there is considerable variation in temperature and ambient light characteristics on leaf surfaces. In this study, we examined; 1) variation in leaf litter temperature and compared these to locations where courting males were found; and 2) reflectance patterns of male spider body parts were compared to the spectra of leaf litter. There was no significant difference between the location temperatures of courting males (22.47 C) and non-courting males (22.56 C) (students t-test, t=0.139; DF=114; P>0.05). Interestingly, the mean location temperature of male spiders was between the means of leaves found in the sun and leaves found in the shade at 22.52 C.  Spectral analysis of spider body parts showed that some parts of the spider appear exceptionally dark (e.g., the lateral view of leg tufts), while other aspects (dorsal median stripe) appear to closely match to the spectra of leaf litter. This revealed that leg tufts contrast with the lighter background of leaf litter, but that dorsal coloration contrasted less with the litter background. These results suggest that wolf spiders maximize contrast and exposure when viewed from the side (by female spiders), while minimizing potential for detection from above (predators) by cryptic coloration. (posted 5 - 4 - 2005)

 

Spider species diversity in some dry forest plants of western Mexico

Authors
Institutions

Pablo Corcuera

Departamento de Biología
UAM-Iztapalapa, MÉXICO

María Luisa Jiménez
Centro de Investigaciones Biológicas del Noroeste
S.C., MÉXICO

Abstract: Spiders  were collected from eight tree and three shrub species in each of two sites in a Mexican dry forest thorough June, July, September, October and November of 1999, and january and abril 2000.  A total of 1349 adult specimens, belonging to 21 species were obtained.  Plant arquitecture and foliage type have been related to spider species richness, abundance and diversity.  We measured relative cover, foliar area, and leaf type and disposition for each plant species in order to determine their influence on the spider community structure.  Number of adults, species richness, dominance (Simpson index) and equitability (Pielou index) were measured for the spiders.  In both sites, small-leaved bipinnate trees and shrubs, particularly the shrub Acacia cymbispina and the tree Prosopis juliflora, had more species as well as higher spider abundances.  Foliar area was negatively correlated with spider abundance in both sites, and to species richness in one of them.  Dominance was particularly high for Croton ciliatoglanduliferus, a widespread shrub typical of disturbed sites in the region, in which the Green Lynx spider Peucetia viridans was abundant. (posted 5- 19 - 2005)

 

The suctorial organ of the Solifugae (Arachnida, Solifugae)

Authors
Institutions

Paula E. Cushing

Department of Zoology,
Denver Museum of Nature & Science
Denver, Colorado USA

Jack O. Brookhart

Hans-Joachim Kleebe

Colorado School of Mines
Golden, Colorado USA

Gary Zito

Peter Payne

 Department of Pathology & Laboratory Medicine
University of British Columbia
Vancouver, British Columbia, CANADA

Abstract: The ability of members of the arachnid order Solifugae to climb smooth, vertical surfaces and the organs involved in this behavior are investigated.  Macroscopic, microscopic, and scanning electron microscopic observations are made of a palpal organ called the suctorial organ. Observations of the behavior but not the microstructure have been made in the past.  Histological examination illustrates the internal gross anatomy of this structure and scanning electron microscopy demonstrates the fine structure in adults of four genera:  Eremobates (Eremobatidae), Eremochelis (Eremobatidae), Eremorhax (Eremobatidae), Ammotrechula (Ammotrechidae), as well as an unidentified late stage immature and third stage instar.  The suctorial organ is most likely primarily used for prey capture in the wild. (posted 5 - 15 - 2005)

 

 

Metals in cuticular structures of Palpigrada, Ricinulei and Schizomida (Arachnida)

Authors
Institutions

Bruce Cutler

Microscopy & Analytical Imaging Laboratory and Department of Ecology & Evolutionary Biology
University of Kansa, Lawrence, KS USA

Lynn McCutchen

Biology Department
Kilgore College, Kilgore, TX USA

Abstract: Specimens of Palpigrada, Ricinulei and Schizomida were examined by energy dispersive x-ray spectroscopy for the presence of metallic elements in cuticular structures. Manganese was found in the largest tooth of the fixed cheliceral finger in a ricinuleid. Zinc was found in the chelicerae, leg and palpal claws and in the palpal tarsal spur of a schizomid. Zinc was also found in the chelicerae and leg claws of a palpigrade. When presence or absence of zinc is added to a cladogram of arachnid orders, the absence of zinc in the Acaromorpha (Acari + Ricinulei) appears to be derived. Similarly the absence of manganese in the Uropygi (Schizomida  + Thelyphonida) may be derived also. (posted 5- 6 - 2005)

 

D, E and F

Unnatural castration in a spider: are environmental pollutants to blame?

Author
Institution

Anne Danielson-François

Ecology and Evolutionary Biology Dept.
Rice University
Houston, TX USA

Abstract: With the 1962 publication of Rachel Carson's Silent Spring, the public began to appreciate more fully the dangers of environmental pollution from pesticides and other anthropogenic chemicals. A particular class of such chemicals, endocrine disruptors, function as sex hormones in vitro and/or in vivo. Environmental estrogens have been implicated in the feminization of male vertebrates, and androgens contribute to imposex in neogastropods. Despite the importance of arthropods in many ecosystems, studies of the effects of these compounds on arthropod species are scarce and there is currently no information available for arachnid taxa. Here, I report the first evidence that anthropogenic chemicals may affect male spiders similarly. Males collected from a polluted site in Louisiana exhibit palp abnormalities that prevent sperm transfer, effectively castrating these individuals. Field-collected adults show a nearly 2:1 ratio of affected to normal males. Lab-reared penultimate-stage males exhibit a 5:1 ratio -- a substantial increase that has profound implications for population dynamics. Possible consequences could include affected populations exhibiting (1) a decreased ability to recover from environmental catastrophes, and (2) increased sensitivity of the population to further exposure by new pollutants, possibly resulting in local population extinction.  Future work will include characterizing the specific chemicals involved by mass spectrometry and high performance liquid chromatography. (posted 5 - 26 - 2005)

 

The spider species of the Great Lakes States

Authors
Institutions

Michael Draney

Department of Natural and Applied Sciences and Cofrin Center for Biodiversity
University of Wisconsin-Green Bay
Green Bay, Wisconsin USA

Petra Sierwald

Zoology Department
The Field Museum
Chicago, Illinois USA

Thomas Prentice
Department of Entomology
University of California
Riverside, California USA

Abstract: Critical analysis of existing spider species lists for Wisconsin, Michigan, Ohio, Indiana and Illinois reveal 899 species recorded from the five-state region (284 genera, 40 families).  Illinois currently has the highest recorded total with 622 species, followed by 571 from Ohio,563 from Michigan, 477 from Wisconsin, and 385 from Indiana.  All non-native, non-established, or otherwise questionable species records were scrutinized and their status is discussed. The most speciose families in the region are Linyphiidae (almost 24% of species), Salticidae (10.3%), Theridiidae (8.9%), Lycosidae (8.8%), and Araneidae (7.7%). The configuration of the five states, as well as the topography and glacial history of the region enabled us to generate predictions of over 400 new state species occurrences based on their known presence within each of the five states, and to produce higher minimum estimates of the actual fauna in each state.  Richness among states is analyzed and found to be primarily dependent on varying degrees of sampling effort.  We feel this work shows that much remains to be learned about the fauna of the Great Lakes region, and we hope this encourages basic faunistic research.  We have created a searchable online database which allows access to all published data, returning currently valid taxa starting from any names previously published from this region.  (posted 5 - 26 - 2005)

 

Responsivity of male Dolomedes triton to dragline silk from females

Authors
Institution

Amber Elaine Ehlman

Department of Biology
College of Notre Dame of Maryland
Baltimore, MD USA

Nancy Kreiter

Abstract: Activities that increase an organism's survival and reproduction are important energetic expenditures for every species. Low density, wandering species must travel long distances in order to locate potential mates. Mechanisms that increase the success of the search and decrease the energetic costs to the animal should be selected for through the evolutionary process. Energy should be allocated where it is most likely to be repaid; in this case in the form of copulation and successful reproduction. We investigated male search tactics in the non-webbuilding spider Dolomedes triton, or fishing spider, which inhabits vegetations around freshwater lakes and ponds in North America. Female D. triton are less active than their male counterparts, which exert considerable time and energy locating and courting females. We tested the hypothesis that males uses cues bound to female dragline silk to locate stationary females. Silk from virgin and mated adult females was extracted from the spinnerets and presented to virgin and mated adult males and the subsequent courtship behaviors including various waves and taps with the legs demonstrated by males were recorded. It was expected that (1) males would expend an approximately equal amount of time and energy courting dragline silk as they would true female spiders (2) males would exhibit preference towards unmated, adult females as this should increase probability of copulation as well as reduce the chance of sexually-induced cannibalism and (3) males cue in on factors among the dragline rather than the presence of silk itself. Variance tests indicate males conserve courtship to pads containing female silk but do not appear to discriminate between virgin or mated silk. (posted 5 - 25 - 2005)

 

Distribution and relations of ground spider's genus Taieria (Araneae, Gnaphosidae) in Australasia

Authors
Institutions

Mariya Fedoryak

Department of General and Experimental Ecology
Chernivtsy National University
Chernivtsy, UKRAINE

Vladimir Ovtcharenko

Department of Natural Sciences
Hostos Community College of The City University of New York
New York, New York USA

Boris Zakharov
Division of Invertebrate Zoology
American Museum of Natural History
New York, New York USA

Abstract: The genus Taieria was described by R. Forster in 1979. Earlier, two species were described by L. Koch (1873) as Drassus erebus and Drassus achropus from New Zealand. R. Forster (1979) showed that those two species were male and female of one species and chose as the valid name Taieria erebus (L. Koch). Additionally, R. Forster described four new species of the genus Taieria from New Zealand: T. elongata, T. kaituna, T. obtusa and T. miranda.

Recently we found one new species of Taieria in New Zealand. Also we found T. erebus and T. kaituna on the Southern Island (both species were recorded before only from the Northern Island) and T. elongata on the Northern Island (earlier known only from the Southern Island). Our revision of Taieria in Australasia showed that this genus is also very common in Australia. We found 16 new species of Taieria in Australia and two in New Guinea. The distribution of Taieria in Australia has an interesting pattern, which shows Eastern Australia more populated and represented by seven species of Taieria. Western Australia is represented by six species, two species of Taieria related to the southern part of Australia and Tasmania. One species is widely distributed across all Australia. It is important to underline that there is no common species of Taieria for New Zealand, Australia and New Guinea. (posted 5 - 25 - 2005, corrected 6 - 8 - 2005)

 

A morphology-based phylogeny of the Habronattus tarsalis species complex and its inconsistency with a molecular phylogeny

Authors
Institution

Steven E. Foldi

Department of Biology, Evolutionary Biology Program Area
San Diego State University
San Diego, CA USA

Marshal Hedin

Abstract: Males of the six species of jumping spiders (Salticidae) belonging to the Habronattus tarsalis group are highly variable morphologically throughout their range in California and surrounding states.  These morphological differences have been used to derive a "species tree" of the relationships between both populations and species.  Neighboring populations in continuous habitat are morphologically more similar to each other than more isolated populations.  Therefore, male morphology appears to be a good tool for examining the relationships of these species and the species tree agrees with typical phylogeographic patterns for California.  However, a gene tree derived from mitochondrial evidence shows divergence only for isolated desert and island populations, but is unable to resolve even some species relationships.  This has lead to the hypothesis that gene flow between neighboring populations in contiguous habitats has caused shared mtDNA sequences, while strong sexual selection has preserved the phylogenetic signal for morphological divergence. Thus, the Habronattus tarsalis group could be a clear example of why different data sets provide variable results. (posted 5- 15 - 2005)

 

G, H and I

Static and dynamic components of male seismic signals reflect influence of past and current condition in the wolf spider Schizocosa ocreata (Araneae: Lycosidae)

Authors
Institution

Jeremy S. Gibson

University of Cincinnati
Department of Biological Sciences
Cincinnati, OH USA

George W. Uetz

Abstract: Courtship displays of male Schizocosa ocreata (Hentz) are multimodal, consisting of visual and seismic signals.  Previous research has shown that male secondary sexual characters (foreleg tufts) are condition-dependent visual signals used in female mate choice.  Here we test the hypothesis that seismic signals are also condition-dependent, through two different approaches.  In the first study, a test of the effect of rearing environment, seismic signals were compared between spiders raised under 3 different conditions: completely in the laboratory (LR), completely in the field (FR) or partially in the field then the laboratory (FL).  A second experimental study tested the effects of current condition on seismic signals.  Adult spiders were collected from the field and placed into two treatment groups, then fed to satiation or starved.  Spiders were recorded 3 times over the course of the experiment.  Rearing environment affected static (e.g. fundamental frequency of signal) and dynamic (e.g. duration of signal) components of seismic signals differently.  Static traits were similar between LR and FR but both differed from FL.   Dynamic traits were similar for FL and FR but differed from LR.  Moreover, static traits did not change over time in response to food availability; however, all dynamic traits did.  These findings suggest that lifetime foraging history and/or habitat and experience contribute to static features of seismic signals, while dynamic features change with current body condition.  This experiment demonstrates that seismic signals in this species are condition-dependent, and contain information that females may be able to use to asses male mate quality. (posted 5- 18 - 2005)

 

Wolf spiders reduce aggression toward conspecifics after repeated encounters

Authors
Institutions

Ryan J. Gifford

Department of Zoology
Miami University
Oxford, Ohio USA

Jill DeVito
Matthew H. Persons
Department of Biology
Susquehanna University
Selinsgrove, Pennsylvania USA
Ann L. Rypstra
Department of Zoology
Miami University
Oxford, Ohio USA

Abstract: The "dear enemy" phenomenon suggests that territorial species should exhibit less aggressive behavior toward familiar neighbors as compared to strangers that they encounter.  We examined whether this phenomena could be operating in populations of the large burrowing wolf spider, Hogna helluo (Araneae, Lycosidae)In a laboratory experiment, we monitored the repeated interactions between adult field-caught females over four consecutive days.  On the fifth day we exposed them to unfamiliar animals and observed that interaction.   There was an increase in the total number of encounters between spiders after repeated exposure but the frequency with which they approached one another with legs raised decreased as did the likelihood of physical contact during encounters.  Thus their interactions appeared much less aggressive after repeated exposure with a conspecific.  However, there was no evidence of a neighbor effect as their behavior toward an unfamiliar animal on day five was similar to their reactions to the familiar animal on day four.   We conclude that, although Hogna females appear to learn to reduce their overall aggression level toward conspecifics in high-density situations, they do not discriminate between individuals they have encountered repeatedly and unfamiliar individuals. (posted 5 - 19 - 2005)

 

Genetic diversity within colonial aggregations of the North American tarantula Aphonoplema hentzi (Theraphosidae) in Texas populations

Authors
Institutions

D.E. Hamilton

Department of Biological Science
Texas Tech University
Lubbock, TX USA

M.E. Janowski-Bell

Department of Biology
Victoria College, Victoria, TX USA

N.E. McIntyre
Department of Biological Science
Texas Tech University
Lubbock, TX USA
L.D. Densmore

Abstract: The Theraphosid genus Aphonopelma belongs to the infraorder Mygalomorphae, a group thought to be relatively primitive and highly conserved morphologically.  Adult females and sub-adult males live in subterranean burrows in informal aggregations commonly referred to as colonies although analysis of aggregations of Aphonopelma hentzi (Girard 1852) in Wilbarger Co., TX showed the burrows to be over rather than under-dispersed indicating the aggregations may simply be the result of habitat condition and not a reflection of behavior (Janowski-Bell 2001).  However, the aggregations may still be matriarchal in nature since although some mygalomorphs have been found to disperse by ballooning (Coyle 1983), theraphosids are not known to do so and this may cause their dispersal distances to be limited in immaturity. Upon maturity, the males disperse, walking from their burrows in search of a mature female, presumably unrelated to the male.  Radio-telemetry work suggests that the dispersal range of Aphonopelma males may be limited to 1-3 km, at least with A. hentzi (Janowski-Bell and Horner 1999). We tested the hypothesis of familial aggregations using two molecular markers from the mitochondrial genome, CO1 and 16S.  Although both showed relatively low levels of diversity the results do not support familial aggregations and instead suggest an ad-hoc assemblage based probably on habitat availability. (posted 5 - 26 - 2005)

 

Molecular evolution and phylogenetic utility of hemocyanin blood protein gene sequences in mygalomorph spiders (Araneae: Mygalomorphae)

Authors
Institutions

Marshal Hedin

Department of Biology
San Diego State University
San Diego, CA USA

Cheryl Hayashi

Department of Biology
University of California
Riverside, CA USA

Abstract: Hemocyanins are hemolymph proteins that facilitate oxygen transport in all major arthropod lineages. The likely basal condition in spiders includes a protein of 620-660 amino acids, duplicated into seven paralogous loci (subunits) that combine to form a 24-mer (4 X 6) quaternary structure. Although paralog structure is fairly conserved in spiders, some lineages reveal dynamic changes in patterns of molecular evolution (e.g., paralog loss and duplication in the RTA clade). To more fully explore patterns of molecular evolution, and assess the phylogenetic utility of this gene family, we have conducted phylogenetic analyses on hemocyanin exon 4 data for a diverse sample of mygalomorphs, and several araneomorphs. Results can be summarized as follows: 1) Mygalomorph sequences fall into seven distinct clades that correspond to the seven well-studied subunits of Aphonopelma. Although not all mygalomorph taxa are represented in each paralog group, this is probably evidence for PCR bias, rather than paralog loss; 2) Trees reconstructed using concatenated and combined (molecules + morphology) matrices recover some expected clades (e.g., Atypoidina), but other larger clades (e.g., Domiothelina) and some families are not recovered as monophyletic; 3) Sequences from taxa representing the RTA clade (Habronattus, Zorocrates, Allocosa, and Cupiennius) are restricted to the subunit g clade. The loss of all paralogs except g, and subsequent duplication within this paralog group, may represent a molecular synapomorphy for this spider clade; 4) Hemocyanins represent, in effect, up to seven independent loci that might be used for molecular phylogenetic analysis in spiders. With development, this gene family has considerable phylogenetic promise. (posted 5 - 13 - 2005)

 

Phylogeography of the Antrodiaetus unicolor species complex (Araneae: Mygalomorphae: Antrodiaetidae)

Authors
Institution

Brent E. Hendrixson

East Carolina University
Department of Biology
Greenville, North Carolina USA

Jason E. Bond

Abstract: Antrodiaetus unicolor (sensu lato) is the most abundant and widespread mygalomorph species in the eastern United States.  Given the dynamic geological history of this region (including orogeny, coastal plain inundation, and glaciation cycles) and the interesting life history characteristics of these spiders (fossorial burrowers, limited dispersal ability), spatial patterns of genetic variation are expected to be diverse and complex.  We investigated the phylogeography of this species complex by sampling over 300 individuals from 100+ populations.  Preliminary assessment of these analyses (based upon COI mtDNA and 28S rRNA; ~1800 bp) suggests a complicated history consisting of recent range expansions, vicariance events, and prolonged periods of isolation and divergence in situ.  Some northern populations (IN, OH, VA, WV) display a genetic signature indicative of recent range expansion into areas previously uninhabitable during the Pleistocene.  Furthermore, there have been multiple independent invasions of these spiders to the coastal plains (i.e., coastal populations are not monophyletic).  Closely related lineages are sometimes disjunct, indicating that ancestral populations became fragmented; this subsequently allowed the sundered populations to diverge substantially from each other.  No mitochondrial haplotypes are shared between populations, and most populations exhibit substantial divergence and genealogical exclusivity.  Secondary contact between distantly related lineages is extremely common and provides strong evidence for multiple codistributed species.  Future research will focus on testing specific biogeographical hypotheses and delimiting species boundaries. (posted 5- 19 - 2005)

 

The rich spider fauna of the Hocking Hills region, Ohio

Authors
Institution

William Hickman

Department of EEO Biology
Ohio State University
Marion, Ohio USA

Richard Bradley

Abstract: The Hocking Hills region is located in Hocking and Fairfield Counties of unglaciated south central Ohio.  The system of hills and valleys were, nevertheless, strongly influenced by the glaciers. Glaciers to the north formed a dam that blocked the northwestward flow of the historic Teays River. The region's drainage was redirected southeast into the relatively newer Ohio River, in the Mississippi drainage.  This history is revealed in the vegetation, which is very diverse, incorporating southern elements characteristic of the western Allegheny plateau and northern remnants from glacial times. This scenic region is dominated by the Black Hand Sandstone which has eroded to form numerous caverns, arches, and recess-caves.  The region is clothed in mature second-growth mixed hardwood forest, hemlock coves, farm fields and pasturelands.  The spider fauna of the Hocking hills is similarly diverse.  A total of 265 species have been documented for the region to date.  Historical collections were made by William Barrows, primarily between 1914 and 1924.  Collections of the Ohio Spider Survey were made between 1994 and 2004.  Only 37% of the spider species were found by both collection efforts;  43% were found exclusively in our recent work and 20% only in the earlier Barrows work.  It is not clear whether or not these differences are due to different sampling methods or possibly actual changes in the spider fauna.(posted 5- 19 - 2005)

 

Variation in the flag gene among Nephila clavipes in Mexico

Authors
Institutions

Linden E. Higgins

Department of Biology
University of Vermont
Burlington VT USA

Sheryl White

Department of Anatomy and Neurobiology
University of Vermont
Burlington VT USA

Juan Nuñez-Farfán

Instituto de Ecología
Universidad Nactional Autonoma de México,
México, D.F., MÉXICO

Jesus Vargas

Abstract: The gene coding for the spider flagelliform silk, Flag, is one of the more recently characterized silk genes, and codes for one of the more recently evolved silks.  Like many silk genes in spiders and other arthropods, the Flag gene has a nested structure:  small glycine and proline rich motifs repeat within larger motifs. In Flag, the larger motifs are ensemble repeats of up to 61 small motifs on either side of a non-repetitive glycine-poor spacer.  Each ensemble repeat corresponds to an individual exon.  Many authors have speculated that the repeating motifs of silk genes may evolve like "minisatellite" DNA, with misalignment during recombination generating variation upon which selection could then act.  This misalignment could also lead to homogenization of the sequences across the repeats, or gene conversion.  The most effective way to test these models is to investigate variation among individuals within a species, but the majority of silk genes that have been sequenced have only been sequenced once for a particular species.  Here, we present a comparison of sequences of one exon from eight individuals from four populations in Mexico. (posted 5 - 20 - 2005)

 

Activity cycles and vertical stratification of spiders in cornfields

Authors
Institution

Ryan Homsher

Miami University
Oxford, Ohio, USA

Alan Cady

Abstract: Spider distributions and abundances across the diel period have been investigated in various row crops but are not well-studied in corn. Furthermore, it is unknown if certain families of spiders prefer specific locations on corn plants, as has been found in other crops. Plants near discrete habitat refugia (small straw piles) in soy and corn fields have been shown to have less insect damage and increased crop yield, but the mechanism behind this "refugia effect" is not clear.  One hypothesis is that spider assemblages associated with refugia help protect plants from herbivory. Thus, a nine-week observational study of spiders on and around plants in six one-half hectare conventionally-tilled corn fields was conducted to determine daily spider activity cycles, their positions on corn plants, and the composition of spider assemblages. Most variability of spider numbers and their community compositions appeared to be related to spider phenology and corn growth stages.  There was a well-defined stratification of spider families on the corn plants. The Lycosidae dominated the ground layer while the Salticidae were most prevalent on the plant tops throughout the season. Other spider families occupying different areas on the plants shifted during the summer. There was an inverse relationship between salticid and thomisid numbers on the plants. Most spiders tended to be active at night, with lycosids and salticids showing a mid-day spike in activity. No significant effects from the presence of refugia were found on spider numbers, but more cursorial spiders tended to be near plants associated with refugia. (posted 5- 24 - 2005)

 

 

J, K and L

Spiders as conservation indicators at two oases in Baja California, Mexico

Authors
Institution

María-Luisa Jiménez

Centro de Investigaciones Biológicas del Noroeste (CIBNOR)
La Paz, Baja California Sur, MEXICO

Miguel Correa

Gisela Nieto

Carlos Palacios

Abstract: Geomorphologic and evolutionary changes in the Baja California Peninsula created many mesic oases. In these habitats, the spider fauna is almost unknown. Two oases were surveyed every two months during 2002-3 to develop an ecological index. Pitfall traps, foliage nets, and hand collections were made along three transects set perpendicular to the oases streams. Of 184 species (138 at San Isidro and 143 at San José de Comondú), 92 were common to both localities. About 45% have nearctic and 22% have neotropical affinity. About 34% are exclusive to Baja California. Diversity of both communities were similar (H' = 3.73 at San Isidro and H' = 3.94 at San José). Morisita's Index was 0.55%. About 6.5% of the species at San Isidro and 6.3% at San José were dominant; whereas rare species represented about 41% at the first locality and 35% at the second. Previously undescribed species numbered 29, as well as one undescribed genus. In mesic areas, about 18% of the species were abundant; in xeric areas, about 39% were abundant. Anyphaena sp. nov. and Hamataliwa grisea were the most abundant species. The many spider species at these oases show that this environment conserves diversity, perhaps from geographic isolation and low anthropogenic impact. The spider species associated with mesic vegetation are probably relict populations of the Pleistocene because they are found in the highland oak-pine forest of the Sierra de la Laguna on the peninsula and highland mesic locations on the mainland of Mexico. (posted 5 - 11 - 2005)

 

Love Bites: Evidence of Coercive Mating in the Brush-Leg Wolf Spider Schizocosa ocreata (Hentz)

Authors
Institution

Julianna L. Johns

University of Cincinnati
Department of Biological Sciences
Cincinnati, OH USA

George W. Uetz

Abstract: Coercive mating is defined as forced copulation when the female is not receptive, (at any point during the interaction or just prior to being mounted), and has been noted in many animals, especially arthropods. Obvious benefits to males who coercively mate include reduced energy cost from prolonged courtship, and an increase in the number of offspring sired. Adult male Brush-legged wolf spiders, Schizocosa ocreata (Hentz), exhibit elaborate courtship displays when presented with adult females and their silk.  In response, females exhibit receptivity behaviors that in most cases determine whether copulation occurs.  However, in trials where females are not receptive, mounting and subsequent copulation sometimes happens.  Upon re-review of videotapes from previous studies of mating in this species, several instances of coercive mating were identified (in 12 out of 92 [13%] of mating trials). In several of these trials, the females were receptive at some point but not directly prior to mounting, and males often physically pulled down non-receptive females (attempting escape from the side of the arena) and copulated with them. Inspection of several male-female pairs in which mating was apparently coercive revealed that during copulation, males used fangs to maintain position in copula. Subsequent examination revealed cuticular wounds oozing hemolymph, which were not seen in consensual matings. The aggressive nature of males in these encounters suggests that further inspection of male behaviors and the potential costs that females may incur should be explored. (posted 5 - 20 - 2005)

 

Revealing cryptic species in the ancient spider genus Hypochilus Marx (Araneae: Hypochilidae)

Authors
Institution

Robin Keith

Department of Biology
San Diego State University
San Diego, CA USA

Marshal Hedin

Abstract: The spider genus Hypochilus is one of the most distinctive groups of spiders in North America. The southern Appalachian fauna, the focus of this work, includes five species (H. gertchi, H. thorelli, H. pococki, H. sheari, and H. coylei) distributed in allopatry from northern Alabama and Georgia to West Virginia. Hypochilus spiders have limited dispersal ability, making them particularly susceptible to geographic range fragmentation. Hypochilus also exhibits morphological and ecological stasis such that evidence for geographic fragmentation may not be readily apparent. To examine comparative patterns of population genetic structure, and discover possible cryptic species, we generated mitochondrial CO1 DNA sequences from a sample of more than 80 populations, representing four of the five eastern species (data for H. thorelli has already been published - Hedin & Wood 2002). Bayesian phylogenetic analyses of these data reveal that all eastern Hypochilus species exhibit patterns of extreme genetic structuring similar to that found in H. thorelli, with extremely low amounts of mitochondrial variation within populations, but high genetic divergence among populations. Isolation by distance analyses support this claim. Additionally, four of the five morphologically defined species are recovered as genetic clades. However, Hypochilus pococki is fragmented into at least five clades, which are geographically-cohesive, show extremely high internal genetic divergences, and are not sister taxa. These observations suggest the presence of "cryptic" species within H. pococki. Recognition of such cryptic lineages is extremely important, as some of these distinct evolutionary units are restricted to as few as three known localities, and may warrant conservation efforts. (posted 5 - 13 - 2005)

 

Spiders in diversified and conventional agroecosystems

Authors
Institutions

Lauren M. Kerzicnik

Department of Bioagricultural Sciences and Pest Management
Colorado State University, Ft. Collins, CO  USA

Frank B. Peairs
Paula E. Cushing
Denver Museum of Nature & Science
Denver, CO  USA

Abstract: Crop management practices influence the biological organisms within an agroecosystem.  In particular, crop diversity can enhance predator populations.  This study will determine if intensive cropping systems will enhance spider species richness and diversity by comparing spider densities in conventional systems (one crop in two years) to diversified systems (two crops in three years).  We hypothesize that a diverse cropping system will have greater species richness and diversity in spider populations than a conventional system.  This is because the diverse rotation has more crop residues, provides more consistent habitats for both predators and prey, and provides more consistent year-round food supplies.  Here we present preliminary results from an ongoing study.  The three field sites for this study are in Akron, Lamar, and Briggsdale, Colorado.  A wheat/fallow rotation was used as a control and compared to the following treatments:  Akron-wheat/corn/fallow, Lamar-wheat/sorghum/fallow, and Briggsdale-wheat/millet/fallow.  Sunflower was also added as a treatment in Briggsdale and Akron because ground predators are known to be diverse and abundant in this crop.  All locations had three plots in a diverse rotation and two plots in a conventional rotation, replicated four times, and organized in a randomized complete block design with repeated measures.  Several sampling methods were employed to collect spiders-pitfall sampling, vortis or suction sampling, and look down sampling.  Preliminary results indicate no consistent patterns among treatment effects for either diversity or richness measures at the family level. (posted 5 - 16 - 2005)

 

The structure and function of sexually dimorphic hair tufts in Dolomedes males

Author
Institution

Nancy A. Kreiter

College of Notre Dame of Maryland
Baltimore, Maryland USA

Abstract: Taxonomic descriptions of the species D. triton generally make reference to a "spinose hump" (Kaston 1981) or a "spiny tubercle" (Carico 1973) located on the hind femur of adult male D. triton. These dark, hairy tufts are obvious to the naked eye and are only found on adult males, never juveniles or adult females. They have been hypothesized to function as clasping structures during copulation.  Light and scanning electron microscopy revealed that these tufts are composed of a diverse population of modified, socketed hairs. Individual hairs are often characterized by enlarged bases, a lumen and an apical pore opening with a protruding extension, perhaps suggesting a sensory function. In order to distinguish between the clasping and sensory hypotheses, juvenile males were brought into the lab until their adult molt. For some of the males, the hair structures were covered with paraffin, eliminating any sensory function. Males were placed with newly molted adult females and their behavior was videotaped and coded. Males did not typically use the structures for clasping females. In fact, most copulations took place with the hind pair of legs placed distant to the female. Paraffin did not influence most courtship parameters, and males with covered hairs were just as likely to mate with a female than were control males. However, copulations were generally shorter in duration when the hairs were covered.  Future studies are planned to continue this investigation. (posted 5 - 26 - 2005)

 

Effects of food deprivation on prey capture behavior in tarantulas (Brachypelma albopilosum)

Authors
Institution

Kevin Kretschmer

Department of Biology
Eastern Michigan University
Ypsilanti, Michigan USA

Cara Shillington

Abstract: Spiders can survive prolonged periods of food deprivation and previous studies suggest that they may alter their foraging activities depending on their level of hunger.  We tested the short-term effects of food deprivation on a tarantula (B. albopilosum) in the laboratory.  These sit-and-wait predators typically remain within burrows from which they strike at passing prey.  In this study, we recorded prey capture ability in relation to hunger level.  Feeding trials were carried out on each animal with an increasing number of days of food deprivation between each trial (1, 3, 5, 7, and 14 days).  All trials were videotaped and from these recordings we determined the total capture time, awareness field, strike distance, attack angle, and relative prey position.  Average capture time decreased substantially as function of time: 97.5s at 1 day and 7.3s at 14 days.  Average strike distance was measured after capture success as the distance from the center of the chelicerae to the nearest cricket appendage.  These data were more variable but over the entire experiment strike distance increased by 28%.  These data suggest that increased hunger levels give rise to increasingly aggressive predator tactics. In addition, there was substantial individual variation in behaviors. (posted 5- 26 - 2005)

 

Patterns of Silk and Excreta Deposition in the Wolf Spider Hogna helluo

Authors
Institutions

Christopher A. Latanich

Biology Department, Susquehanna University
Selinsgrove, Pennsylvania USA

Rebecca L. Holler

Biology Department, Elizabethtown College
Elizabethtown, Pennsylvania USA

Ann L. Rypstra
Department of Zoology, Miami University
Hamilton, Ohio USA
Matthew H. Persons
Biology Department, Susquehanna University
Selinsgrove, Pennsylvania USA

Abstract: We measured the context and pattern of silk and excreta deposition in the wolf spider Hogna helluo. Hogna were allowed to move freely for four hours on individual grid-bearing 80 mm dia. paper disks. We then quantified dragline silk coverage, number of attachment disks and excreta produced on each sheet. We compared differences in silk and excreta deposition as a function of sex, developmental status, clutch, female reproductive status (virgin and mated), female diet (cannibalistic/not), and the presence or absence of chemical cues from crickets (Acheta domesticus). Silk deposition (both dragline and attachment discs) was highly variable and did not differ significantly by clutch among juvenile spiders. Dragline silk production increased significantly among mature females compared to various juvenile stages (early, mid and penultimate instars) and adult males.  Surprisingly, we found no significant reduction in dragline deposition among females after mating suggesting either another function independent of mating, or that female Hogna may continue to advertise to acquire multiple mates. We found no significant difference in dragline or attachment disc deposition among cannibals and non-cannibals. Excreta deposition was highly controlled and context specific, significantly increasing in the presence of chemical cues from house crickets. Attachment disks were produced similarly by all developmental stages and both sexes. Adult females significantly decreased attachment disk production in the presence of prey cues. Since prey of wolf spiders use silk information as an early warning for the presence of predators, reduced silk production may increase foraging effectiveness and mitigate antipredator responses in prey. (posted 5 - 13 - 2005)

 

Phylogenetic implications of mutation biases in arachnid mitochondrial genomes

Author
Institution

Stuart J. Longhorn

Department of Biology
Portland State University
Portland, OR USA

Susan E. Masta

Abstract: Mitochondrial sequences have been widely used to infer phylogenies within arachnids, but few studies have compared the evolution and systematic utility of mitochondrial genes among different arachnid orders. Here, we use new mitochondrial genomes from several arachnids to evaluate phylogenetic relationships between the major arachnid lineages such as scorpions, spiders, amblypigids, and ticks. Given our taxon sampling, phylogenetic analyses of the 13 mitochondrial protein-coding genes typically support the monophyly of each arachnid order. In the spiders (Araneae), we find strong support for the Mygalomorph-Araneomorph sister-group (Opisthothelae), to the exclusion of Mesothelae. However, a subset of protein-coding genes (transcribed on the alpha-strand) do not strongly support the Araneae, and recover unexpected relationships among arachnid orders. We compare nucleotide composition at synonymous sites, and show that true spiders (Opisthothelideae) have reversed comositional bias in several mitochondrial genes, which are overly rich in T or G nucleotides. In contrast, most other arachnids, including spiders of the suborder Mesothelae, show mostly A or C nucleotides at these sites. We show that these differences in codon usage can influence the outcome of phylogenetic analyses, particularly as scorpions show the same (reversed) nucleotide bias as true spiders, as do varroid mites. Here we evaluate the utility of different data coding schemes to mitigate the effect of the codon usage biases on phylogenies based on mitochondrial genomes of arachnids. (posted 5 - 26 - 2005)

 

M, N and O

 

Rare genomic changes as phylogenetic characters for arachnid systematics

Author
Institution

Susan E. Masta

Department of Biology
Portland State University
Portland, OR USA

Abstract: The evolutionary relationships among the arachnid orders are not agreed upon, and morphological and sequence data have yielded conflicting phylogenetic hypotheses. We have been sequencing mitochondrial genomes from representatives of all arachnid orders to obtain new data that may aid in resolving relationships. I have been examining genomic data to look for changes in the genome that occur very rarely and hence may be useful for resolving ancient divergences. Such changes include gene rearrangements, changes in the secondary and tertiary structures of the gene products, and changes in gene processing. Here I present new mitochondrial genome data from eight arachnids from Araneae, Amblypygi, Uropygi, Scorpiones, and Solifugae. I find unusual truncated transfer RNA genes in multiple orders of arachnids, such that the size of the inferred tRNAs are about two-thirds those of typical mitochondrial tRNAs. These truncated genes are inferred to code for tRNAs that lack the canonical cloverleaf secondary structure. Additionally, there is a substantial reduction in the size of the large ribosomal RNA gene among multiple arachnid orders, with an inferred loss of multiple stems and helices from the secondary structure. Finally, gene order differs among some of the orders. I discuss the evolutionary and systematic implications for each of these rare genomic changes. (posted 5 - 26 - 2005)

 

Cold temperature tolerance and distribution of the brown recluse (Loxosceles reclusa) in Illinois

Authors
Institution

Alex Maywright

Department of Biology
Monmouth College
Monmouth, IL 61462

Ken Cramer

Abstract: The temperature tolerance of the brown recluse spider, Loxosceles reclusa, has been briefly describe by Hite et al. (1966) as having the range of 4.5°C to 43.3°C. In various laboratory experiments the cold tolerance of L.reclusa was tested with temperatures ranging from 3° to -14°C.  Three experimental methods facilitated in determining the cold tolerance of the brown recluse.  First, an experiment was setup to test a 4h exposure to a certain test temperature during a 16h period. Second was to test if the recluse spider produced a silk retreat when exposed to simulated winter temperatures. The final experiment tested the effects of a 90d exposure to a constant test temperature of 0° C and -5° C.  While determining the cold tolerance in a controlled environment, temperature data loggers were used to recorded leaf and grass litter temperatures for 3 months that were compared to ambient air temperatures to describe a correlation between ambient and litter temperatures in northern Illinois. With the gathered information I was able to determine a theoretical distribution of L. reclusa throughout Illinois. (posted 5- 18 - 2005)

 

Prey availability on the blackbrush, Acacia rigidula, for the scorpion, Centruroides vittatus

Authors
Institution

C. Neal McReynolds

Department of Biology and Chemistry
Texas A&M International University
Laredo, Texas USA

Julianna Quintanilla

Oscar Ramos

Abstract: The scorpion, Centruroides vittatus, often feeds in blackbrush, Acacia rigidula, and on caterpillars (Lepidoptera).  What factors affect the availability of caterpillars on blackbrush?  Does caterpillar availability influence the foraging behavior of C. vittatus?  The availability of caterpillars was sampled with a beating sheet to beat blackbrush from May 20, 2004 to May 12, 2005 on the campus of Texas A&M International University in Laredo, Texas.  Blackbrush with scorpions were compared to blackbrush with no scorpions present.  Scorpion activity was observed during the same period to compare to caterpillar availability.  The season, temperature and precipitation all had significant effects on the number of caterpillars per sample.  The average number of caterpillars per sample was higher during September, lower at temperatures < 20 °C, and higher with precipitation greater than 10 cm during the prior two weeks.  Scorpions in blackbrush did not select a blackbrush with significantly higher caterpillar numbers than blackbrush sampled at random.  Scorpion microhabitat use changed significantly with the average number of caterpillars per sample per night (caterpillar classes).  However, the use of blackbrush was not different among the caterpillar classes.  The proportion of scorpions with prey did not change significantly among the caterpillar classes.  However, the proportion of scorpions with caterpillars as prey did increase with a higher average number of caterpillars per sample per night.  The foraging behavior of C. vittatus does not appear to change to take advantage of the availability of caterpillars in blackbrush, but the opportunistic scorpions feed on caterpillars when available. (posted 5 - 24 - 2005, corrected 6 - 8- 2005)

 

The systematics of widow spiders (Araneae, Theridiidae, Latrodectus): Recent progress and future prospects

Authors
Institutions

Jeremy A. Miller

Department of Entomology, California Academy of Sciences
875 Howard Street, San Francisco, California, 94103, USA

Jessica Garb

Department of Biology, University of California
Riverside, California, 92521, USA

Ted Schultz

Department of Entomology
National Museum of Natural History
Smithsonian Institution
Washington, DC 20013-7012, USA

Jonathan A. Coddington

Abstract: New molecular sequence data from over 70 Latrodectus specimens provides evidence for the evolution of the genus and the circumscription of Latrodectus species. This study builds on the first molecular phylogeny of Latrodectus, which was based on a single mitochondrial gene (cytochrome oxidase I). Most specimens from that analysis plus many new specimens were sequenced for two nuclear genes: histone 3 and 28S ribosomal RNA. These data are added to two higher-level studies, one on theridiid genera, and one on Hawaiian linyphiids. This later study provides a calibration point for estimating the ages of historic events, such as the origin of Latrodectus. Future sequencing work and plans for a global monograph of Latrodectus based on morphological, molecular, and behavioral data are previewed. (posted 5 - 12 - 2005)

 

The effect of juvenile experience on adult female mating preferences in Schizocosa ocreata (Hentz)

Authors
Institution

Jenai Milliser

Department of Biological Sciences
University of Cincinnati
Cincinnati, OH USA

George Uetz

Abstract: In spiders as well as other animals, species recognition and mating success are linked to female preferences for male traits and courtship displays.  Although social experience is known to influence adult mate recognition and female preferences in some vertebrate animals, relatively little is known about such effects in invertebrates.  Recently, Hebets (2003) demonstrated an effect of juvenile exposure on adult mate preference in the wolf spider Schizocosa uetzi. In a two-part study, we investigated whether juvenile female experience with male courtship influences adult female mate recognition using the well-studied brush-legged wolf spider, S. ocreata (Hentz).  In the first study, penultimate S. ocreata females were exposed multiply to bimodal (visual + vibratory) courtship of one of two conspecific male phenotypes (males with decorative leg tufts removed; 2. males with intact tufts). In the second study, penultimate S. ocreata females were exposed multiply to bimodal conspecific or heterospecific (S. rovneri) male courtship. Upon maturing, exposed females were paired with an adult male of the same or opposite phenotype/species to which they had been previously exposed and were observed to determine receptivity and willingness to copulate.  Exposure to different male phenotypes (tufts/no tufts) had no significant effect on female receptivity or female willingness to mate.  However, exposure to conspecific vs. heterospecific courtship did influence female receptivity.  The role of juvenile exposure and plasticity in female mate recognition and choice behavior in these spiders will be discussed. (posted 5- 24 - 2005)

 

Identification of glutamic acid decarboxylase (GAD) isoform immunoreactivity in the central nervous system of the barn spider, Araneus cavaticus

Authors
Institutions

Myung-Jin Moon

Department of Biological Sciences
Dankook University
Cheonan 330-714, KOREA

Edward K. Tillinghast
Department of Zoology
University of New Hampshire
Durham, NH USA

Abstract: The gamma-aminobutyric acid (GABA) has long been considered an inhibitory neurotransmitter in the central nervous system (CNS) of both vertebrates and arthropods. The glutamic acid decarboxylase (GAD) catalyzes the conversion of L-glutamate to GABA. As the GAD has a restricted tissue distribution, it is highly expressed in the cytoplasm of GABAergic neurons in the CNS. However it is also present in other non-neuronal tissues such as testis, oviduct and ovary. Recently, there were reports that a GABA-like immunocytochemical reactivity and a ninhydrin-positive GABA derivative, GABamide, exists in the visual ganglia and in the water-soluble fraction of the spider web respectively. So, this experiment initiated to identify exact distribution of the GAD isoform immunoreactivity in the CNS of the spider to reveal the ecophysiological significance of GABA for spider's behavior. (posted 5- 24 - 2005)

 

Factors affecting substrate choice of crab spiderlings over their lifetime

Author
Institution

Douglass H. Morse

Ecology & Evolutionary Biology
Brown University, Providence, RI USA

Abstract: Crab spiders (Misumena vatia: Thomisidae) choose many different hunting sites over their lifetime, shifting from innate responses to certain substrates as naïve spiderlings to direct responses to prey as adults. Since the flowers used as hunting sites continually change over the season, the spiders regularly have to make new decisions.  Spiderlings retain a constant preference for goldenrod over aster or wild carrot from their first encounter until at least three weeks later.  They also prefer wild carrot to wild parsnip, a rare and patchy umbellifer that attracts far more prey than the closely related carrot.  By the fourth instar, though free-living individuals in the field exhibit preferences between daisies and buttercups that probably reflect their likely experience, naïve fourth instars reared in the laboratory initially have no preferences.  Free-ranging penultimates have acquired the strong prey-dependent substrate choice characteristic of adults.  These changes in behavior over ontogeny appear to be gradual, rather than of a stepped nature. (posted 5- 19 - 2005)

 

Analysis of the conserved N-terminal domains in major ampullate spider silk proteins

Authors
Institutions

Dagmara Motriuk-Smith

Molecular Biology Department
University of Wyoming
Laramie, Wyoming USA

Alyson Smith
Randolph V. Lewis
Cheryl Y. Hayashi
Department of Biology
University of California
Riverside, California USA

Abstract: Major ampullate silk, also known as dragline silk, is one of the strongest biomaterials known.  This silk is composed of two proteins Major Ampullate Spidroin 1 (MaSp1) and Major Ampullate Spidroin 2 (MaSp2).  Only partial cDNA sequences have been obtained so neither the entire sequence nor the N-terminal domain have been characterized for either protein.  Here we report the sequence of the N-terminal region of major ampullate silk proteins from three spider species: Argiope trifasciata, Latrodectus geometricus, and Nephila inaurata madagascariensis.  The amino acid sequences were determined from genomic DNA.  Northern blotting experiments verified that the predicted 5' end of the transcript is present in fibroin mRNA.  Silk protein N-termini can be distinguished from repetitive regions by a unique amino acid sequence.  Analyses comparing the level of identity of these N-termini show that it is the most conserved part of the silk proteins.  Two DNA sequence motifs identified upstream of the putative transcription start site are potential silk fibroin promoter elements.  Silk protein N-terminal sequences may provide information useful in a better understanding of biochemistry of silk fiber formation and developing a more efficient production of synthetic silk protein.  DNA and amino acid sequences can also be used as new markers to identify silk proteins and their evolutionary relationships. (posted 5 - 18 - 2005)

 

The evolution of spider prey capture thread and the limitations of cribellar thread

Author
Institution

Brent D. Opell

Biological Sciences, Virginia Tech
Blacksburg, Virginia USA

Abstract: Spider evolution has been marked by new mechanisms of capture thread adhesion and by the enhancement of existing mechanisms.  The origin of the large Infraorder Araneomorphae coincided with the appearance of aerial capture webs and cribellar capture threads that increase the web's ability to retain prey.  Cribellar threads produced by members of the basal family Hypochilidae are formed of cylindrical fibrils that rely on van der Waals forces to adhere to smooth surfaces and on snagging to hold rough surfaces.  In contrast, members of the remaining 21 families of cribellate spiders (with the exception of Filistatidae) produce nodded fibrils.  These nodded fibrils generate stronger capillary forces in addition to the adhesive forces of cylindrical fibrils.  The origin of orb-weaving spiders was marked by an increase in cribellar thread stickiness, achieved by threads formed of a greater number of fibrils.  A major increase in capture thread stickiness occurred in araneoid orb-weavers, where viscous threads replaced cribellar threads.  This increase may be explained, at least in part, by the ability of these viscous threads to overcome two limitations to the stickiness of cribellar threads.  More of the material invested in a viscous thread appears to contribute to its stickiness.  Viscous thread architecture appears to overcome the tendency of a cribellar thread to generate effective adhesion only at the edges of its contact with a surface. (posted 5 - 16 - 2005)

 

Ground spiders (Gnaphosidae) in Australia: a new characteristic of the subfamily Zelotinae

Author
Institution

Vladimir  Ovtsharenko

Department of Natural Sciences
Hostos Community College of The City University of New York

New York, New York USA

Abstract: One of the major characteristics of the subfamily Zelotinae is a preening comb on the ventral surface of the distal part of the metatarsus of  the third (and occasionally the fourth) leg. Australian Zelotinae lack a distinctive preening comb and have only a preening brush, making it necessary to find additional morphological characteristics for all subfamily of Zelotinae. Our recent SEM research shows that this subfamily has a very distinctive characteristic: all representatives of Zelotinae lack covering setae on the body, with all surface of the cuticle covered only with short and strong mechanoreceptive setae. This morphological characteristic is common in Zelotinae from the Northern Hemisphere as well as Australia. (posted 5 - 25 - 2005)

 

P, Q and R

Does bad taxonomy serve conservation purposes? The case of the Cicurina cueva complex (Araneae: Dictynidae) in the vicinity of Austin (Travis Co.) Texas

Authors
Institution

Pierre Paquin

Department of Biology
San Diego State University
San Diego, CA USA

Marshal Hedin

Abstract: Urban development in central Texas is a threat to many habitats, especially caves. About a dozen cave-restricted arthropod species are protected by the Endangered Species Act, while many others are classified as species of concern. The later category includes Cicurina cueva Gertsch, an eyeless spider known from only two caves in the vicinity of Austin. A proposition for a new highway threatens the ecological integrity of Flint Ridge Cave, one of the two known localities for C. cueva. Correctly assessing the distribution and species limits of this taxon appears crucial for any conservation decisions. An intense sampling effort resulted in the collection of Cicurina spp. from ~70 caves in Travis, Hays and Williamson counties. About 1kb of mtDNA (CO1) was sequenced for 170 spiders and the phylogenetic approach of Paquin & Hedin (2004) was used to assign species names to juveniles. Likelihood and Bayesian analysis gave similar results and extended the occurrence of C. cueva from two to ~20 adjacent caves. These results suggest that C. cueva, C. bandida and C. reyesi are the same biological entity. Furthermore, spermathecal variation is not correlated with geography or mtDNA phylogeny, providing further support for synonymy. The genetic structure of C. cueva populations indicates restricted gene flow, as expected for cave organisms. Some conservationists perceive species rarity based on inadequate taxonomy or lack of collections as beneficial as it increases the biological uniqueness of certain caves. However, long-term conservation strategies require adequate taxonomic knowledge, which is still, unfortunately, largely deficient. (posted 5 - 17 - 2005)

 

Nitrogen enrichment in grasslands alters spider community structure

Authors
Institutions

L. Brian Patrick

Department of Biological Sciences
Kent State University
Kent, OH USA

Lauchlan H. Fraser

Department of Natural Resource Science
Thompson Rivers University
Kamloops, BC  CANADA

Mark W. Kershner
Department of Biological Sciences
Kent State University
Kent, OH USA

Abstract:  Nitrogen enrichment in terrestrial ecosystems significantly increases plant biomass while significantly decreasing plant species richness.  However, the effects of these well-documented, nutrient-mediated changes to primary producers on the remainder of the food web have received little attention in terrestrial ecosystems. To address this, we manipulated nutrient availability and plant detritus in grasslands at the Bath Nature Preserve in northeastern Ohio to investigate whether nutrient-mediated changes in plants resulted in increased arthropod biomass and decreased arthropod species richness.  While documenting changes in plant biomass and species richness during 2002-2004, we used pitfall traps to sample the epigeal arthropod community.  Within 20m diameter circular plots in the grassland (an annually mown, former hay meadow), we manipulated nitrogen (fertilizer added vs. no fertilizer) and plant detritus (following annual mowing in autumn; plant litter removed vs. left in place) to form a blocked 2x2 factorial design with six replicates (N = 24 experimental plots).  Four pitfall traps per plot (N = 96 traps) were used to sample arthropods for two-week-open intervals alternated with two-week-closed intervals during late May through mid-August of each year.  Within fertilized plots the three dominant wandering spider families (Araneae: Lycosidae, Gnaphosidae, and Clubionidae) significantly increased in biomass, significantly decreased in species richness, and shifted community composition for both biomass and individual counts, essentially losing the largest bodied species.  Thus, these results highly correlate with effects of nitrogen enrichment on plant species richness and biomass, clearly demonstrating the effects of eutrophication in terrestrial ecosystems. (posted 5 - 26 - 2005)

 

Variation in leg and pedipalp setae in tarantulas from arboreal and terrestrial habitats

Authors
Institution

Ben Philip

Eastern Michigan University
Ypsilanti, Michigan  USA

Cara Shillington
Glenn Walker

Abstract: Tarantulas are well-known for their size and hairiness.  Although these hairs may appear uniform, they often differ at the microscopic level in both form and function.  For example, spiders use the hairs on their body as an important sensory conduit for detecting both mechanical and chemical signals.  Because habitats and life styles vary for different species, we hypothesized that there would be differences in the hairs found on the legs and pedipalps of (1) different species and, (2) arboreal and terrestrial species.  We used scanning electron microscopy to examine the pedipalps and legs of both arboreal (Avicularia avicularia and Poecilotheria regalis) and terrestrial species (Aphonopelma smithi and Brachypelma vagans).  On the pedipalps of the two terrestrial species we found some very distinct smooth hairs interspersed among the more typical feathered hairs.  These smooth hairs were not found on the arboreal species, nor were they seen on the first pair of legs of either terrestrial species.  Further, the ventral sides of the tarsus of the legs and pedipalps in both terrestrial and arboreal spiders were covered with scopula hairs.  Although the shape at the base of these scopulae was similar between the two groups, the distal ends varied; the arboreal species had a much flatter distal end compared to the sharply curved end of the terrestrial tarantulas. (posted 5 - 19 - 2005)

 

Blood-sucking spiders

Authors
Institutions

Simon D. Pollard

Canterbury Museum
Christchurch, NEW ZEALAND

Robert R. Jackson

School of Biological Sciences
U
niversity of Canterbury
Christchurch, NEW ZEALAND

Abstract: Using specialized mouthparts, mosquitoes pierce vertebrate skin and gain access to a rich food - blood. No spiders are known to feed on vertebrate blood in this straight-forward way, but Evarcha culicivora (Salticidae), a jumping spider from the Lake Victoria region of Kenya and Uganda feeds indirectly on blood. It does this by finding and capturing its preferred prey, blood-fed female mosquitoes. In other words, the mosquito finds and collects the blood and then E. culicivora finds and eats the mosquito. Using first and third instar E. culicivora feeding on Anopheles gambiae (fed on human blood), we examined the mechanisms used by the spider to extract blood from the mosquito. Smaller instars were used because they were less likely to obscure parts of the prey while feeding. A potential barrier to the spider extracting blood is that the blood meal which is stored in the abdomen of the mosquito is surrounded by a peritrophic membrane which thickens over time. We found that E culicivora almost always started feeding from the thorax and using suction from the combined action of pharyngeal muscles and a sucking stomach, could rupture the membrane of recently fed mosquitoes and extract blood. However, after 24 hours, the peritrophic membrane is too thick to be ruptured by suction from the thorax and instead E. culicivora would rupture the membrane directly using suction and its fangs. (posted 5- 25 - 2005)

 

Effects of detritus subsidy on the abundance and diversity of spiders in an agricultural ecosystem

Authors
Institutions

Jennifer G. Riem

Department of Zoology
Miami University, Oxford, Ohio, USA

Christopher M. Buddle

Department of Natural Resource Sciences
McGill University, St. Anne de Bellevue, Québec, CANADA

Ann L. Rypstra
Department of Zoology
Miami University, Hamilton, Ohio, USA

Abstract: Productivity has been shown to have a strong effect on species diversity in some ecosystems. Soybean fields are cyclical ephemeral ecosystems in which an interaction between the annual recolonization and competition may drive spider abundance and diversity. Because spiders are food-limited, insect density, which is an estimate of prey availability, is a measure of productivity available to spiders. The purpose of our study was to investigate the species diversity and community composition of ground-dwelling spiders across the season and in response to a range of productivity levels. In this study we added detritus to plots in agricultural fields in order to impose an experimental productivity range. Detritus was added at four levels in June and July, and insects and spiders were sampled in July, August, and September. Preliminary results suggest that insect abundance did not respond to detrital subsidies. Insect abundance peaked in August, and spider abundance was higher in August and September than in July. In August, overall spider abundance, and wolf spider (Lycosidae) abundance in particular, were correlated with ambient insect density. Overall spider abundance was related to sampling time but spider abundance was not related to detritus application. Similarly non-metric multidimensional scaling analysis at the family level suggests that community structure was influenced by sampling time but not detritus application Our results suggest that overall abundance and family composition were more closely tied to seasonal shifts than productivity. (posted 5 - 13 - 2005)

 

Do males of the wolf spider Schizocosa ocreata (Hentz) (Araneae: Lycosidae) exhibit social facilitation of courtship?

Authors
Institutions

J. Andrew Roberts

Department of Evolution, Ecology, and Organismal Biology
The Ohio State University Newark
Newark, Ohio USA

Emily Galbraith
Department of Biological Sciences
University of Cincinnati
Cincinnati, Ohio USA
Jenai Milliser
George W. Uetz

Abstract: Theory predicts that males will exhibit alternative mating tactics that maximize overall mating success.  Tactics that exploit dyadic interactions within a communication network could contribute to increased success by reducing investment in mate searching or increasing efficiency of mate quality evaluation.  One potential alternative tactic for males in scramble competition mating systems, such as that found in the brush legged wolf spider, Schizocosa ocreata, includes eavesdropping on the courtship of nearby competing males to increase the likelihood of primary encounter with a cryptic potential mate.  We tested the possibility that male S. ocreata exhibit social facilitation of courtship behaviors using a combination of live behavioral trials and video playback to isolate the visual signaling modality of courtship in male competitors.  The results of both live behavioral and video playback experiments indicate that male S. ocreata, when exposed to the visual component of conspecific male courtship behavior, can discern the presence of another individual whether that individual is courting or not.  However, they do not show evidence of social facilitation of courtship or chemoexploratory behaviors in response to visual cues as there was no significant change in the total number or mean duration of these behaviors during or after any stimulus exposure.  While visual signals play a role in mate choice in S. ocreata, in male/male interactions they may serve to draw attention to vibratory signals, and thus further work involving multi-modal signaling will be necessary before social facilitation of courtship can be ruled out for this species. (posted 5 - 20 - 2005)

 

Individual recognition in the amblypygid Phrynus marginemaculatus

Authors
Institution

Ginevra L. Ryman

ESPM - Insect Biology
University of California Berkeley
Berkeley, CA USA

Andrew J. Spence

Eileen A. Hebets

Abstract: Individual recognition is extremely important in many animal taxa, especially in the context of repeated agonistic interactions. During the day, adult amblypygids (Phrynus marginemaculatus) reside individually under limestone rocks. At night, individuals leave their rock to forage, typically returning at sunrise. Male P. marginemaculatus are known to engage in ritualized agonistic interactions and individuals seem able to recognize their individual rock. To discover if P. marginemaculatus is capable of individual recognition, we constructed an arena with two artificial entrances opening to potential hide-outs. In a series of four laboratory experiments, cages were attached to the entrances in the following manner: (1) only their own cage, (2) their own cage and an empty cage, (3) their own cage and another individual's cage with whom they had no experience (unknown), and (4) an unknown cage and the cage of an individual with whom they recently had an agonistic encounter. Individuals in experiment 2 and 3 were most likely to enter the first opening they encountered. However, in experiment 2, individuals that explored both entrances tended to enter their own cage, suggesting individual recognition. After staged agonistic encounters, individuals were used in the cage preference trial for experiment 4. Of the individuals that explored both entrances, 100% of the losers entered the unknown cage while 83% of the winners entered their previous opponent��s cage, suggesting that losers recognized and discriminated against the cages of opponents which had defeated them, and winners recognized and favored cages of opponents which they had defeated. (posted 5 - 26 - 2005)

 

Silk reduces plant damage caused by pest insects

Authors
Institutions

A. L. Rypstra

Department of Zoology
Miami University
Hamilton, Ohio USA

C. M. Buddle
Department of Natural Resource Sciences
McGill University, St. Anne de Bellevue, Québec, CANADA

Abstract: Spiders dominate the terrestrial predatory arthropod community and can have strong effects on potential prey even in situations where there is no possibility of predation. Since spiders are ubiquitous predators and they all produce silk, we explored whether the silk dragline could serve as a signal causing pest insects to reduce their activity or relocate.  We hypothesized that spiders could reduce plant damage caused by herbivores if the insects reacted to the silk left behind by the spider.  We applied freshly produced spider silk and commercially available silkworm silk to snap bean leaves enclosed with either Japanese Beetles or Mexican bean beetles in the laboratory and in field enclosures.  In addition, we applied both types of silk to individual leaves of unenclosed leaves in the field.   In separate experiments we applied silkworm silk to all the leaves of an entire plant and either enclosed the plant with beetles or left it exposed so that it could experience natural herbivory.  In all cases, leaves treated with experienced less leaf damage.  These results suggest that silk may be an important signal to insects that a predator is foraging in the area.  Thus, silk may play an important role in integrated pest management or biological control. (posted 5 - 17 - 2005)

 

S, T, U and V

Habitat choice and an intraguild predator lead to a reduction in foraging efficiency in the wolf spider, Pardosa milvina (Araneae, Lycosidae)

Authors
Institutions

Jason M. Schmidt

Department of Zoology
Miami University
Oxford, Ohio USA

Jill DeVito
Matt Persons
Biology Department
Susquehanna University
Selinsgrove, Pennsylvania USA
Ann Rypstra
Department of Zoology
Miami University
Hamilton, Ohio USA

Abstract: Spiders often prefer more structurally complex habitats because there is more protection from predators, higher prey abundance and more suitable microhabitat conditions.  In the laboratory we designed experiments to determine if the wolf spider, Pardosa milvina (Araneae, Lycosidae) had a habitat preference, if that habitat preference changed in the presence of cues from the intraguild predator, Hogna helluo (Araneae, Lycosidae) and if habitat and predator presence affected foraging efficiency. In a choice test, Pardosa consistently preferred the more complex straw over dirt but the contamination of the straw with Hogna cues eliminated that preference. Both habitat complexity and the presence of Hogna had negative effects on Pardosa foraging efficiency.  These results demonstrate that Pardosa prefers the more complex substrate but that they shift their habitat use and foraging in the presence of the potential predator. In addition the cost of high levels of habitat complexity in the form of a straw matrix would be that spiders spend more time looking for prey. The results of this study provide a richer understanding of the habitat associations of wolf spiders.   Further research will help untangle the specific aspects of complex habitats that Pardosa milvina are selecting. (posted 5 - 20 - 2005)

 

Habitat and behavioral characteristics associated with habitat selection in Antrodiaetus unicolor: results from preliminary lab and field investigations

Author
Institution

Chad D. Schone

Department of Entomology
Ohio State University
Columbus, Ohio USA

Abstract: Although habitat selection is the underlying process that determines much of the ecology of an organism, as well as ultimately influencing its fitness, its attributes for many spider species remain undescribed.  One species that has gained my attention is the folding-door spider species, Antrodieatus unicolor.  Among the few mygalomorph species that has a distribution into the temperate regions of the Midwestern U.S, A. unicolor appears limited to very specialized habitats within these regions.  Presumably, this species is extremely sedentary; consequently, selection of habitat is crucial to its success.  To determine suitable characteristics in habitat selection, I conducted a series of preliminary investigations into preferred soil properties, population densities, and settlement decisions
In my initial inquiry into populations in southern Ohio, I found that larger aggregations, along with positive mass and length gains, were associated with slightly higher surface humidity and slightly lower surface temperature compared to sites that did not contain naturally occurring aggregations.  Subsurface soil humidity and pH appear to have little influence on individual growth.  Additionally, while individuals exhibited a preference for burrowing in the absence of leaf litter, there are no strong indications that individuals make burrowing decisions based on the presence or absence of other individuals.
Further, there is some evidence to suggest that individuals create multiple burrows over their lifespan, often abandoning previous burrows soon after molting occurs.  Future experiments and observations will focus on decision-making factors regarding habitat selection, shadow competition, limits of population densities and habitat availability, conspecific attraction, prey availability, and dispersive ability.
(posted 5- 19 - 2005)

 

Phylogenetic analysis of the arachnid orders using morphological characters

Author
Institution

Jeffrey W. Shultz

Department of Entomology
University of Maryland
College Park, Maryland USA

Abstract: Despite ever-increasing reliance on molecules by systematists, morphology still contributes phylogenetic information and is necessary for accommodating fossils in systematic analysis as well as reconstructing organismal evolution. Here 194 binary and unordered multistate characters were coded for 52 chelicerate taxa (37 extant and 15 fossil) from original observations and literature review. Parsimony analyses were performed on the extant taxa alone and on all taxa. Neontological data recovered four arachnid lineages -- 1) Palpigradi, 2) Tetrapulmonata (Araneae (Amblypygi, Uropygi)), Acaromorpha (Acariformes (Anactinotrichida, Ricinulei)) and Dromopoda (Opiliones + Scorpiones) (Pseudoscorpiones + Solifugae) -- whose interrelationships were unresolved in strict consensus. Successive weighting resolved the following relationships (((Palpigradi, Tetrapulmonata) Acaromorpha) Dromopoda). Significantly, Opiliones and Scorpiones were recovered as sister groups and Acari was recovered as diphyletic. Due to analytical problems caused by unknown states in fossil taxa, the full data set was analyzed using the strict consensus from neontological data as a backbone constraint. The unweighted data produced 14069 trees, with no resolution among the four lineages recovered by neontological data. Successive weighting, both with and without backbone constraint, produced a topology consistent with neontological results. Among fossils, Haptopoda was recovered as the sister group to Palpigradi + Tetrapulmonata; Trigonotarbida as sister group to extant Tetrapulmonata.  This analysis introduces many new characters, redefines "traditional" characters and corrects errors perpetuated by uncritical recycling of data. The results highlight strengths and weaknesses in our understanding of arachnid phylogeny. (posted 5- 19 - 2005)

 

Preliminary analysis of mating in Leiobunum nigripes (Opiliones) and diversification of male reproductive structures in Leiobunum

Author
Institution

Jeffrey W. Shultz

Department of Entomology
University of Maryland
College Park, Maryland USA

Abstract: Systematists rely on male-specific structures in circumscribing species and species groups in Leiobunum. Presence of paired, distally open, chitinous sacs located subterminally on the penis appears to be primitive but are modified as bulbs in some groups and lost in others. Genital morphology and mating in a sacculate species L. nigripes were examined to determine functions that might explain genital diversification. Sacs in the retracted penis receive "nozzles" that drain large accessory glands; sacs are typically filled with fluid. Females display acceptance by orienting to the male with mouth open. The male runs towards the female and clasps her at the trochanter of leg II with his palps. He rapidly inserts the penis in her mouth (apparently delivering a nuptial gift from the sacs), withdraws the penis and begins to probe for the opening of her genital operculum. The female manipulates the inflated basal part of the penis with her chelicerae. After a variable time, the female opens the operculum and the male assumes a "head up" position. Male reorientation exposes the "nozzles" and the female feeds on secretions. Interaction between penis and ovipositor occurs inside the female genital chamber and cannot be seen. Examination of reproductive structures in other species suggests that genital diversification is associated with mechanisms by which males control the quantity of gift fluid offered to females, either by regulating amounts of the primary gift (bulbate strategy) or facultatively substituting coercive restraint for secondary gift (lanceolate strategy) through enhanced clasping mechanisms. This scenario attributes genital diversification to natural rather than sexual selection and suggests that evolutionary plasticity is an inherent property of genitalia. (posted 5- 19 - 2005)

 

Environmental effects on prey-capture behavior for Androctonus crassicauda (Scorpiones: Buthidae) in north-central Iraq, Operation Iraqi Freedom II

Author
Institutions

Alexander K. Stewart

216th Engineer Combat Battalion
1st Infantry Division, Operation Iraqi Freedom II
and
Department of Geology
University of Cincinnati
Cincinnati, Ohio USA

Abstract: Prey-capture behavior is a fundamental characteristic in understanding a scorpion's narrow gamut of stereotypical behaviors.  Quantitative studies of these behaviors, however, are rare and, when studied, are generally (by necessity) performed in a laboratory.  This laboratory setting allows easier setup, care, control and analysis than a field setting.  Interestingly, one can combine the benefits of a laboratory with the field enviornment; thereby, generating a third, intermediate study location - the "outdoor" laboratory.

By contrasting prey-capture conditions in both indoor and outdoor laboratories, demonstratable differences in the behavior of Androctonus crassicauda (Olivier, 1807) have been observed. For instance, the total capture time (handling time prior to ingestion), amount consumed, sting frequency, travel time and inactive periods differ between the indoor and outdoor laboratories. These differences suggest that the indoor laboratory may be inappropriate for observing natural scorpion behaviors. Hence, a scorpion's prey-capture behavior should, when amenable, be studied in an outdoor-type laboratory.

By using habitat- and locale-specific outdoor pens, substratum and ambient (local) environmental changes, scorpions are stressed in a manner corresponding to their natural environment.  Despite problems with habitat/locale-specific studies in some areas of the world, it can be relatively easy for observers, who must cohabitate with indigenous scorpion species, to study and observe their behaviors in an easy-to-control, field-like setting. (posted 5-5-2005)

 

The Promyrmekiaphila World According to GARP

Authors
Institution

Amy K. Stockman

Department of Biology
East Carolina University
Greenville, NC

David Beamer
Jason E. Bond

Abstract: One of the primary goals of any systematic, taxonomic, or biodiversity study is the characterization of species distributions.  While museum collection data and field observation are important for ascertaining distributional ranges, they are seldom exhaustive.  The primary objective of this study is to use existing collection records to more accurately estimate the distribution of the spider genus Promyrmekiaphila (Araneae: Mygalomorphae: Cyrtaucheniidae) in central and northern California.  The approach we employ is a geospatial analysis that uses the artificial intelligence method GARP (Genetic Algorithm for Rule-set Prediction).  GARP uses four different rule-sets to infer correlations between geographic information system (GIS) layers representing known species localities and a set of environmental parameters (e.g. elevation and annual precipitation).  The algorithm determines which environmental parameters are significant factors in circumscribing species distribution and provides predictive models for present-day population locations.   A GARP spatial analysis based on seven environmental layers and 42 known localities of Promyrmekiaphila predicted the occurrence of Promyrmekiaphila throughout northern/central California.  These predictions were then field tested to assess the accuracy of the model.  (posted 5 - 17 - 2005)

 

Fates of male tarantulas (Aphonopelma anax) during the breeding season

Authors
Institution

Todd B. Stoltey

Eastern Michigan University
Ypsilanti, Michigan  USA

Cara Shillington

Abstract: At maturity, male tarantulas (Aphonopelma anax) leave their burrows and sedentary lifestyles to actively search for spatially scattered females in a non-aggressive scramble competition polygyny.  Mate searching activities expose males to a greater risk of predation, high environmental temperatures, dehydration, and potential cannibalism by females.  In this study 16 mature males were fitted with radio-tags and tracked over the course of the breeding season which occurs from late May to July.  Males experienced a mortality of 50%; 75% from Tarantula Hawk wasps (Pepsis sp.).  Mate searching was primarily nocturnal and crepuscular but activity often extended into periods of full daylight.  Males rarely used burrows for daytime retreats and most often utilized partially concealed shaded areas under brush.  Activity occurring during daylight hours and poorly concealed daytime retreats could expose males to an increased risk of predation from diurnal predators like Tarantula Hawk wasps.  This may explain the high mortality from Tarantula Hawk wasps.  Additional males will be radio-tagged and tracked during the 2005 breeding season. (posted 5 - 25 - 2005)

 

Burrows, nests and retreats; a comparison of structures built by wolf spiders in the southeastern U.S.A.

Authors
Institution

Gail Stratton

University of Mississippi
University, MS USA

Amy Nicholas

Abstract: Among wolf spiders in the USA, burrow construction and use is best known in the obligate burrowers, the Geolycosa.  However, earlier literature noted several species of wolf spiders that may sometimes be found in burrows or retreats.  We have done a comparative study of the structures made by wolf spiders.  In the laboratory, individual wolf spiders from more than 18 species were placed in containers 14 cm wide x 21 cm tall and were provided with a minimum of 7 cm of top soil and 8 cm of dried grass.  Following burrow or nest construction, we photographed the structure, removed the spider and made a cast of the structure with Plaster of Paris.  With the cast, we were able to measure length, width and volume of the excavation.  We have now documented tubular burrows for Artosa littoralis, Hogna annexa,  Hogna sp. helluo group sp. "A" , Rabidosa rabida, R. punctulata, R. carrana, as well as for Geolycosa missouriensis, G. fatifera and G. rogersi.   Bowl-shaped excavations or nests, often with silken covers have been seen "Allocosa"(=Hogna) georgicola, Schizocosa saltatrix, Trochosa acompa, Rabidosa hentzi, Hogna lenta sp. group and Hogna helluo.   We report on the variety of shapes and sizes of the structures as well as the above ground turrets or silken covers.  Understanding the evolution of the behaviors of building retreats will require both a detailed study of the behavior and a much more resolved phylogeny of wolf spiders than now exits.  However, this study points to the complexity and variety of burrowing behaviors. (posted 5- 24 - 2005)

 

Mechanics and energetics of excavation by burrowing wolf spiders

Authors
Institutions

Robert B. Suter

Department of Biology
Vassar College
Poughkeepsie, New York USA

Gail E. Stratton

Department of Biology
University of Mississippi
Oxford, Mississippi USA

Patricia R. Miller

Department of Biology
Northwestern Mississippi Community College,
Senatobia, Mississippi USA

Abstract: Burrowing wolf spiders (Lycosidae, Geolycosa sp.) excavate vertical burrows and inhabit them throughout their lives or, in the case of males, until they mature and wander in search of mates.  We studied three species, G. fatifera, G. missouriensis, and G. rogersi, with the aim of understanding how, and at what expense, the burrowing is accomplished.  Normal and high-speed videography, coupled with scanning electron microscopy, revealed (a) that the convex surfaces of the fangs, together, constitute the digging tool, (b) that boluses of soil are transported to the burrow entrance on the anterior surfaces of the chelicerae, held there by the pedipalps, and (c) that each bolus is either incorporated into the growing turret or flung away, propelled by the forelegs.  To elucidate the energetics of burrow construction, we first measured burrow volumes and then assessed the costs associated with dislodging, elevating and throwing the known volumes of soil.  A typical G. missouriensis burrow, at a volume of 30.3 ± 6.7 ml and a depth of 15.8 ± 1.8 cm, required the removal of 1195 boluses each weighing about 34 mg.  The aggregate dislodging cost was close to 2.5 Joules, the work against gravity necessary to raise all of the boluses to the surface was about 0.2 Joules, and the aggregate cost of flinging the boluses was close to 0.02 Joules.  In soil that is difficult to dislodge, like that in which we found G fatifera, the excavation cost per bolus is about 3 times as high. (posted 5 - 12 - 2005)

 

Insights into the distribution and phylogeography of the enigmatic opilionid, Fumontana deprehendor Shear (Opiliones: Laniatores: Triaenonychidae)

Authors
Institution

Steven M. Thomas

Department of Biology
San Diego State University
San Diego, CA USA

Marshal Hedin

Abstract: The opilionid species Fumontana deprehendor Shear 1977 (Laniatores: Triaenonychidae) is formally known from only four specimens from two published localities, both old-growth forest sites in the southern Appalachian mountains. Its distinctive morphology combined with its perceived rarity make F. deprehendor one of the most unique opilionid species in North America. Although other triaenonychids are known from the Pacific Northwest, Fumontana appears most closely related to Gondwanan taxa, suggesting an extremely old and relictual distribution. In August 2004, we undertook a focused sampling effort throughout the southern Appalachian mountains to better understand the true abundance and distribution of this monotypic genus. After uncovering a much more complete and perhaps true distribution of the genus, the phylogeographic and species status was analyzed via a combination of molecular and morphological data. Molecular phylogenies generated using Bayesian analysis of mitochondrial and nuclear sequence data suggest four allopatric, geographically cohesive molecular clades. Interestingly, these clades show an almost complete lack of internal divergence, which is surprising given the predicted limited dispersal ability of these animals. The geographic distribution of these clades corresponds remarkably well to patterns seen in other cryophilic arthropods of the region (e.g., Trechus beetles), suggesting a shared pattern of vicariance. Preliminary morphological data from representative male specimens, consisting of drawings of the palps and legs 1+2, measurements, and SEM images of penises, were analyzed to look for concordance with the recovered molecular clades. Conservation implications, the possibility of cryptic speciation, and future research directions are discussed in light of the new data provided. (posted 5 - 13 - 2005)

 

Molecular characterization and Evolutionary study of spider tubuliform (eggcase) silk protein

Authors
Institution

Maozhen Tian

Department of Molecular Biology
University of Wyoming
Laramie, Wyoming USA

Randolph V. Lewis

Abstract:  As a result of hundreds of millions of years of evolution, orb-web weaving spiders have developed the use of seven different silks produced by different abdominal glands for various functions. Tubuliform silk (eggcase silk) is unique among these spider silks due to its high serine and very low glycine content. In addition, tubuliform silk is the only silk produced just during a short period of time,  the reproductive season, in the spider's life. To understand the molecular characteristics of the proteins composing this silk, we constructed tubuliform gland specific cDNA libraries from three different spider families, Nephila clavipes, Argiope aurantia and Araneus gemmoides. Sequencing of tubuliform silk cDNAs reveals the repetitive architecture of its coding sequence and novel amino acid motifs. The inferred protein, tubuliform spidroin 1 (TuSp1) contains highly homogenized repeats in all three spiders. Amino acid composition comparison of the predicted tubuliform silk protein sequence to tubuliform gland protein indicates that TuSp1 is the major component of tubuliform silk. Repeat unit alignment of TuSp1 among three spiders shows high sequence conservation among tubuliform silk protein orthologue groups. Comparative analysis demonstrates that TuSp1 represents a new orthologue in spider silk gene family. (posted 5 - 19 - 2005)

 

The Effect of Male-Male Competition and Information Availability on the Courtship and Copulatory Behavior of the Wolf Spider Schizocosa ocreata (Araneae: Lycosidae)

Authors
Institutions

Erin E. Tipton

Biology Department, Susquehanna University
Selinsgrove, Pennsylvania USA

Ann L. Rypstra

Department of Zoology, Miami University
Hamilton, Ohio USA

Matthew H. Persons

Biology Department, Susquehanna University
Selinsgrove, Pennsylvania USA

Abstract: We measured the effect and interaction of male-male competition and differential access to information about female mating status (presence/absence of pheromone-laden female silk) on male courtship latency, courtship intensity, mating success, and copulation duration.  We created six treatments utilizing combinations of the presence or absence of a second "spectator" male and the presence or absence of pheromone-laden female silk.  Within 30-minute trials (N = 86 trials), the second male "spectator" was physically isolated from the female via a transparent barrier but received visual and seismic cues in all trials and chemical cues from the female in some treatments. If male-male competition mediates courtship and mating behavior, we expected that the presence of a second male would decrease courtship latency, increase courtship intensity, and increase copulation duration compared to treatments without an additional male. Further, second males that have access to silk and visual/seismic information about females would court more vigorously and for a longer period of time.  This would induce higher courtship rates and copulation duration among males with direct access to the female.  We found that in general, female advertisements toward males via silk had a much larger impact on male and perhaps female behavior than the presence of a spectator male.  However, we found evidence that when spectator males also had access to female silk, this had a significant priming or synergistic effect on the other male's behavior across some treatments resulting in increased copulation duration, increased courtship intensity, and shorter latency to court. (posted 5 - 13 - 2005)

 

Modified piriform silk glands in adult male Mimetus (Araneae, Mimetidae)

Authors
Institution
Mark A. Townley

Department of Zoology
University of New Hampshire
Durham, NH, USA

Edward K. Tillinghast

Abstract: In addition to numerous (range 35-63) typical piriform gland spigots, each anterior lateral spinneret (ALS) of adult male Mimetus puritanus Chamberlin 1923 (N = 5 pairs of ALS) and Mimetus notius Chamberlin 1923 (N = 2 pairs of ALS) contains 2 spigots that we interpret as serving modified piriform glands. This pair of modified piriform spigots occurs on a clearly demarcated patch of smooth cuticle, immediately lateral to the major ampullate spigot/nubbin/tartipore complex, within an indentation formed by the typical piriform spigot spinning field. The modified piriform spigots are wider and have larger caliber openings than the typical piriform spigots. They are absent in adult females and penultimate instar males. Presumably, products of the silk glands served by these spigots play some role in reproduction. It may be of taxonomic value to determine if the modified piriform spigots occur beyond the genus Mimetus. (posted 4 - 27 -2005)

 

Effect of starvation and web removal on composition of sticky droplets in orb webs (Araneae, Araneidae)

Authors
Institution
Mark A. Townley

Department of Zoology
University of New Hampshire
Durham, NH, USA

Edward K. Tillinghast

Abstract: Orb web sticky droplets contain a variety of small compounds that often account for half or more of the dry weight of the web. In three araneid species (Araneus cavaticus, Argiope aurantia, Argiope trifasciata), we investigated how starvation affects the composition of the droplets and tested the prediction that organic droplet compounds more readily synthesized by the spider decline less rapidly during fasting than those less readily synthesized. We estimated the ability of spiders to synthesize the organic compounds using radiolabeled metabolites. Many changes observed with fasting were consistent with the prediction. Especially conspicuous was the apparent partial replacement of N-acetylputrescine by the similar but more readily synthesized 4-aminobutyramide (GABamide) in starving A. trifasciata. Other changes, however, such as a decline in alanine in starving A. trifasciata, were not predicted from the synthetic capacity measurements. Moreover, feeding controls often exhibited changes similar to those observed with starving spiders. This suggests that starvation alone did not account for all shifts in composition in starving spiders and that factors shared by starving and feeding spiders also contributed to these changes. Perhaps most important, webs were removed for analysis each day in both starving and feeding groups, thereby denying spiders the opportunity to recover web constituents by ingesting old webs. Another possibility is that some changes that did result from starvation were similarly exhibited by feeding spiders because the latter experienced shortages for web construction as a result of allocating resources to growth, oviposition, or heavier webs . (posted 5 - 16 -2005)

 

Multi-modal communication and mate choice in wolf spiders: results of studies with live males and audio/video playback

Authors
Institutions

George W. Uetz

Dept. of Biology
University of Cincinnati
Cincinnati, OH  45221 USA

J. Andrew Roberts

Department of EEOB
The Ohio State University -- Newark
Newark, OH  43055 USA

Phil Taylor

Department of Psychology
Macquarie University
Sydney, Australia

Abstract: Male Schizocosa ocreata exhibit complex multi-component and multi-modal (visual and seismic) signals in courtship.  Previous and current studies of this species suggest female responses to courtship modes are equivalent, but variation in isolated visual signals (decorative leg tufts) and seismic signals (substratum vibration) influences female receptivity. To examine redundancy and possible interaction of male courtship modes in female mate choice, we used isolated and combined stimuli from males and video/audio playback.  In cue isolation studies with live males, responses of females varied significantly with stimulus.  Latency to orient was shortest for multimodal cues, longer for visual cues, and longest for seismic cues.  Female receptivity was greater when females were presented with multi-modal cues compared to isolated modes, which did not differ from each other.  Female spiders were presented with replicated playback stimuli in two experiments: 1) unaltered male video exemplars with and without seismic cues, and seismic cues alone; 2) male video exemplars with enlarged and reduced leg tufts, with and without seismic cues.  Results of the first experiment confirm earlier studies - female response to multimodal cues is greatest, but is lower and equivalent for isolated modes.  Experiments manipulating tuft size show greater female receptivity with larger tufts regardless of the presence/absence of seismic cues. However, latency to orient to the male stimulus was influenced by tuft size and the interaction of tuft size and seismic cues; females responded more quickly to stimuli with larger tufts accompanied by seismic cues.  These results support a multi-function "super-signal" hypothesis for multi-modal communication. (posted 5 - 24 - 2005)

 

The brown recluse challenge: arachnids submitted as possible brown recluse spiders nationwide

Author
Institution

Richard S. Vetter

Department of Entomology
University of California Riverside
Riverside, California USA

Abstract: An internet offer was made to identify any spider in the United States perceived to be a brown recluse spider, Loxosceles reclusa Gertsch and Mulaik.  Over a five-year period, a total of 1,773 specimens from 49 states were submitted, representing three arachnid orders (Araneae, Solifugae, Opiliones).  The identifiable spiders consisted of 37 families, 88 genera and 158 recognizable species.   Participants from states at least half within the known brown recluse distribution submitted Loxosceles spiders 32 to 89% of the time, except Louisiana and Mississippi with no Loxosceles submissions.  From 25 of 29 states completely or almost completely outside of the range of Loxosceles spiders, no recluse spiders were submitted.  Only two discoveries of brown recluses and two of the worldwide tramp species L. rufescens were submitted from nonendemic Loxosceles areas.  States on distribution margins of brown recluse or other native Loxosceles spiders were intermediate in their Loxosceles submissions.   This study showed that 1) the general public perceives brown recluses to occur throughout the United States, and 2) brown recluse spiders are frequently submitted from endemic states, almost never from non-endemic states, and, therefore, are virtually limited to their known distributions. This study corroborates opinions that diagnosis of brown recluse spider bites are best restricted to areas historically supporting proven, widespread populations of Loxosceles spiders.  This research has been accepted as a Forum article by the Journal of Medical Entomology and should be published in Autumn 2005. (posted 4-25-2005)

 

The effects of preservatives and temperatures on arachnid DNA

Authors
Institutions

Cor J. Vink

Department of Biology
San Diego State University
San Diego, CA USA

Steven M. Thomas
Pierre Paquin
Cheryl Y. Hayashi
Department of Biology
University of California, Riverside
Riverside, CA USA
Marshal Hedin
Department of Biology
San Diego State University
San Diego, CA USA

Abstract: We tested the effects of different preservatives and temperatures on the yield of spider and scorpion DNA useable for PCR amplification. Our experiment was designed to simulate conditions in the field and laboratory over a six week time period, testing the preservatives RNAlater®, propylene glycol, and various ethanol concentrations. Three replicates of each preservation treatment were stored at five different temperature treatments; -80 °C, -20 °C, 2-4 °C, 19-24 °C, and 40 °C. DNA was extracted and quality was assessed by electrophoresis on mini-gels, and by PCR amplification of high copy mitochondrial DNA fragments (cytochrome oxidase subunit I) and low copy nuclear DNA fragments (actin). Results show that RNAlater® and propylene glycol are significantly better than the other preservatives for high quality DNA preservation and that tissue is best stored at -80 °C or -20 °C. Storage in 95% ethanol is appropriate if specimens are stored at -20 °C or -80 °C. We believe our results can help guide biologists in choosing preservatives and temperatures for DNA-based research on arachnids, other arthropods and invertebrates in general. We also tested the long-term effects of temperature and preservatives on arachnid tissue, which was stored in either 70% EtOH, 100% EtOH or RNAlater® at  -80 °C, -20 °C, 2-4 °C, and 19-24 °C. These results further illustrates that tissue should be stored at - 20 °C or less and that RNAlater® outperforms ethanol. (posted 5 - 25 - 2005)

 

 

W, X, Y and Z

Information transfer and spider silk

Author
Institution

Stim Wilcox

Department of Biological Sciences
Binghamton University
Binghamton, NY USA

Abstract: Spider silk is involved in vibratory, visual, and pheromonal information and disinformation transfer in a wide variety of contexts, including mating and agonistic behavior, species-specific identification, prey luring/capture, predator avoidance and deterrence, orientation on the web, and ecolocation. Information transfer using silk has apparently directly shaped the evolution of web design in some species, where physical properties of silk, as they relate to information transfer, are involved in web design. (posted 5-20-2005)

 

Control of copulation duration in a wolf spider (Araneae, Lycosidae)

Authors
Institutions

Shawn M. Wilder

Department of Zoology
Miami University
Oxford, OH USA

Ann L. Rypstra
Department of Zoology
Miami University
Hamilton, OH USA

Abstract: Copulation duration can have an important impact on male fertilization success.  We examined if males or females seemed to control copulation duration by exploring the relationship between age, size and condition of each sex and mating time in the wolf spider Hogna helluo (Araneae, Lycosidae).  Male age and size were linearly related to copulation duration but no female characteristics were significant.  Further analyses revealed that the linear relationships were an artifact of the group of long copulations influencing the regression.  Logistic regression revealed that male age was positively and male size negatively related to the probability of a male engaging in a long copulation.  After accounting for differences in long and typical copulations, male condition was negatively related to copulation duration.  Males that engaged in long copulations were more likely to be cannibalized following mating.  Our data provides support for the hypothesis that males exert the primary influence on copulation duration in H. helluo.  Older, smaller and poor condition males may engage in longer copulations to increase their paternity with the current female because they may have a lower chance of escaping postcopulatory sexual cannibalism or surviving to find another female. (posted 5- 20 - 2005)

 

The effects of leg loss and regeneration on prey capture rate, capture efficiency and sensory detection in Schizocosa ocreata

Authors
Institution

Kerri M. Wrinn

Department of Biological Sciences
University of Cincinnati
Cincinnati, OH  USA

George W. Uetz

Abstract: Previous laboratory experiments have shown no effects of leg autotomy on prey capture in adult wolf spiders.  However, these effects may not be the same for juveniles, which have different foraging patterns and are able to regenerate lost appendages.  Additionally, none of the previous studies addressed prey capture in a natural setting.  Recent studies have shown that juvenile wolf spiders in the field with missing/regenerating legs have reduced body condition.  For these reasons, this study tested the effects of autotomy and regeneration on prey capture in juvenile Schizocosa ocreata wolf spiders in both artificial and semi-natural settings.  Spiders were tested for capture efficiency (i.e., measures of latency to orient to, capture and subdue prey) in a 15 cm diameter circular arena with cricket prey.  Sensory detection through vibration (i.e., measures of accuracy of orientation) was also tested by placing spiders in the same type of arena but visually isolating them from their prey.  Subsequent analyses showed no effects of autotomy or regeneration on any measures of prey capture efficiency.  Similarly, spiders' vibratory sensory abilities were not significantly affected by autotomy or regeneration.  However, when spiders were tested in a semi-natural habitat (a mesocosm filled with leaf litter), individuals with a missing or regenerating leg had reduced prey capture rates.  This suggests that while negative effects of autotomy and regeneration do not appear to be directly attributable to mechanical or sensory impacts on foraging, they may only be apparent in more complex environments such as the spider would encounter in nature. (posted 5- 18 - 2005; modified 6 - 9 -2005)

 

Evidence for dragline mediated mate location in the wolf spider, Hogna helluo (Araneae, Lycosidae)

Authors
Institutions

Montra Yazdani

Department of Zoology
Miami University
Oxford, Ohio USA

Elizabeth A. Heltzel
Matthew H. Persons

Department of Biology
Susquehanna University

Selinsgrove, Pennsylvania USA

Ann L. Rypstra
Department of Zoology
Miami University
Oxford, Ohio USA

Abstract: Many spiders produce sex pheromones that carry information on species identity, maturity and mating status of potential mates.  In previous studies we have failed to uncover evidence of airborne pheromones in the wolf spider, Hogna helluo (Araneae, Lycosidae). The purpose of our study was to determine if males of that species locate and follow female silk draglines. Virgin lab-raised adult male and female Hogna were used in our experiments. Silk was collected from females and placed in single lines on a 90x40cm arena. Male Hogna, were then placed in the arena and monitored for 30 minutes. The amount of time spent close to the silk, number of passes made over the silk strands, and any courtship behavior displayed were recorded. Silkworm silk was used in separate trials as a control. Male Hogna spent more time associated with female silk and made more passes across female silk than with silkworm silk. These results suggest that there are pheromones associated with female draglines of Hogna helluo and that males are likely to use those draglines to locate reproductively receptive females.. (posted 5 - 19 - 2005)

 

Web architecture in the western black widow spider (Latrodectus hesperus) in relation to prey availability

Authors
Institution

Jacquelyn M. Zevenbergen

Department of Biology
University of Akron
Akron, OH USA

Steven A. Schulz

Todd A. Blackledge

Abstract: Tradeoffs between prey capture and predator defense commonly cause changes in behavior. For instance, starved orb-weaving spiders sometimes construct larger webs, using thinner silk threads, than fed spiders. Within the Theridiidae, the orb web has been transformed into seemingly chaotic cobwebs, which depend upon tangled sheets and gumfooted threads to capture prey. We hypothesized that cobweb spiders with more food resources would invest more silk in webs than starved spiders and that the allocation of silk to gumfooted threads versus the sheet would change with resource availability. To test these hypotheses, we initially fed one group of black widow spiders for eight days while starving a second group. We then quantified web architectures and switched the feeding regimes between groups for a further eight days before repeating the quantification. We found that black widow spiders with more food resources were heavier than starved spiders and that heavier spiders invested more silk in webs than lighter spiders. We also found that starved spiders invested more silk in prey capture elements, sheets and gumfooted threads, while fed spiders directed resources into the three-dimensional tangle. We suggest that fed spiders are allocating silk resources toward the spinning of a defensive three-dimensional tangle, while starved spiders allocate effort toward foraging. (posted 5 - 24 - 2005)

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American Arachnological Society 2005
29th Annual Meetiing
University of Akron
Akron, Ohio USA